Ideas please for waterproof sheet/throw/blanket to top my bed

[Dieu]

If anyone can successfully answer this, then you will have my gorgeous Shih Tzu pup and I as friends for life, as you will have saved mine!
I will keep this thread short, but as explained in my previous one, I stupidly introduced my 13 week old pup to the joys of sleeping in my bed before fully toilet trained. Now he understandably won't settle for any other sleeping arrangement.
Now I would like to find a solution which will enable him to sleep on top of my bed, but not pee through my duvet in the process.
I'm thinking maybe a large waterproof blanket or throw, to cover my kingsize bed. I am fairly houseproud, and live in a flat so anyone can see into my bedroom if the door's open. So nothing too ugly or pawprinty would be smashing. Maybe there's a large, plain soft throw out there with a fully waterproof backing. If it isn't too costly, perfect.
A Google search hasn't brought up too much, but the names Kudos and Tuffie have come up.
Any recommendations would be fantastic, even if it's something different that I haven't thought of.
Thank you SO much for your help.

If you are handy with a sewing machine (or have a friendly dry cleaner who does repairs) you could look at using a waterproof mattress cover from Ikea (v cheap, about £20 for a king size, I think) and cutting it up and sewing it to your throw of choice. So you would have a waterproof backing but a lovely throw as well.

You could try taking a cheap shower curtain and sew / tack it on to the inside of a duvet cover ( just tack the corners and maybe the middle just to keep it in place) and then put the duvet in so it's under the shower curtain as the shower curtain is inside the duvet cover you won't see it.
If an accident does happen your duvet will stay dry and all you'll have to wash is the duvet cover. A simple cheap solution until your dog is sleeping through the night and able to hold its bladder till morning.

Lots of picnic blankets have waterproof backing and plenty of designs to choose from, and reasonable prices too.

I also came on to suggest a picnic blanket. Some fab ones out there, all sorts of designs to suit all tastes.

My one days you can't wash it, but I bung it in a 40 degree wash and it's been fine.

Remember that they sometimes can take a wee while to dry, so might be an option to have 2? I say this as we're going through night time loo training with one of the kids, and the waterproof sheets take an age to dry, so i got another one so I can make up the bed quickly. Not the same as your problem really, but thought I'd mention it!

Some fantastic ideas here everyone - thank you all very much indeed. I am pleased to report that he slept last night in his (waterproof) dog bed, on top of my bed. He tried to sneak on to the duvet a few times, but was happy enough to be popped back into his bed (which was placed right beside me on my bed!). Success ... long may it last!