I would say you can probably keep using the Close for a couple more months before it gets really uncomfortable, which gives you a bit of time to look around.
Your main options, really, are an SSC, a mei tai, woven wrap, or framed carrier, and probably one of the first two options would be best for you depending on what your priorities are (ease of use vs flexibility). On facing outwards, I really wouldn't recommend this as an option, firstly because it places the baby in the "crotch dangler" position where their hips are improperly supported and all their weight is directly on their crotch, which is not great for their development to be carried like this for long periods, and secondly because it's the least comfortable position to carry in for you, because of aforementioned crotch-dangling. It would basically be suspending all his weight off your shoulders, which you definitely won't be able to do for much longer. (If you're using the Close Carrier facing out now, try facing in but slightly shifted to one side, with one arm in, one arm out - this gives them a view out but they can still come back to you to hide if feeling overhelmed and should be comfier for you.)
So I'd go for a good supportive sling which you can easily do back carries in, which you'll probably have to switch to over the next few months anyway. If you are looking to use one in the winter, consider looking at a babywearing coat, because most of the slings you can get will be uncomfortable if he is wearing a coat and can't always be worn over your own coat. I found a normal coat in XXL size was absolutely fine but did look a bit scruffy/strange. You can also use a large fleece and just cut an extra head hole in which looks less weird.
SSCs (Soft Structured Carriers) - Look a bit like a rucksack or a larger version of the baby bjorn type carriers, they have clips rather than tie straps. These are probably your best bet if you have a wriggler and have never done back carries before. They can go over or under a coat, I find a coat on DS makes it difficult (but not impossible, and I suspect I wasn't adjusting it enough to compensate) to get him in properly though if he is wearing one. They can wear bulky trousers and shoes, though, because the straps make it easier. Polar fleece is non-bulky but warm, and if he is against your body then you will share body heat too, which helps. Look at the Patapum (toddler size) and the Boba 2G, as these will last you longer and are a lot more padded. I have the toddler Patapum and can still carry 3 year old DS comfortably. The Ergo is the most well-known of the SSCs but TBH I don't rate them if you plan to keep using after a year as they are particularly short in the back. There is also the Beco which is slightly different in that it has a panel of fabric between parent and child. This has a fold down part on the backrest though which means that you can start using it sooner. The toddler carriers are often not recommended for use before a year or so, because the backs will often come up past the baby's head which can be frustrating for them. It's hard to tell at what age the sling will be suitable - if you want to start using it ASAP it might be better to get one which is more universally sized. Avoid mega-cheapies or unbranded ones from ebay as they are usually crap and sometimes dangerous. The Patapum is the best value for money, and does lack some features due to this. Worth googling all the brands and seeing what others come up too.
Mei Tai - similar to an SSC, except you wrap and tie the straps a bit like a wrap (but more structured). You can get different sizes of these. They tend to come in really nice patterns. Generally speaking, wider straps = more supportive/comfortable. The best of the best are Wrap conversions but they are very expensive. It's worth looking on ukbabywearingswap (yahoo group) or other forums which have FSOT boards, particularly "natural" or "attachment" parenting type places. You can nearly always fold the backs of these to shorten them if you wanted to buy a toddler sized one, but use it now. I'm not up to speed with different makes of these, but one brand I know quite well is Pouchlings which is run by a mum local to me, almost all of my sling-wearing friends seem to have at least one of her slings and they are very good quality and supportive. Hopefully other posters will recommend other Mei Tais. I don't think you can wear these over a coat but I'm not sure.
Woven wrap - These are very supportive and extremely versatile, but I found difficult to use for back carries as I hadn't started early enough. General wisdom seems to be if you leave it until after 6 months, it's too late. I wish I'd known this earlier as I spent ages wondering why DS wouldn't just lie there placidly like the other babies and screamed, wriggled, held on desperately and tried to fight it! I could have saved us both a lot of frustration. The pros of a woven wrap are that they are very warm, if you wanted to use during winter. With wraps you will pay a lot for a decent one. The best tend to be the German brands like Stochenwiege and Didymos.
Framed carrier - you've probably seen these before. Advantage is that they can be worn over coats and DC can wear bulky coats, also some can be used as a sort of portable high chair. Disadvantages - heavier, a LOT bulkier to wear and store, often expensive, can feel less "connected" to child (no snuggly cuddles en route!) only one way to wear it.
If you happen to have a slingmeet locally I think that would be your best bet, it's likely you'd be able to see SSCs, Mei Tais and wraps there to compare in real life rather than on a website.