Ok, so as you've said you don't want to suddenly move to mixed feeding as that will play havoc with your supply. What you want to do is pick one time when you want to do a bottle feed and stick to that. All other feeds boob, cluster feeding or not. You probably will find at first that you get engorged when you miss this feed, so you might want to pick a time when she usually has a smallish gap for the first one, and /or express off a small amount by hand to relieve the pressure.
Over time you can add other bottle feeds to your daily routine, to keep supply it's best to still be breastfeeding regularly, so e.g. alternate feeds between breast and bottle rather than trying to substitute two adjacent feeds. It might be worth writing down what you want the routine to look like and then work on replacing one feed at a time starting with the biggest gap. If you keep the bottle feeds regular and use your supply and demand hormones to adapt to change in her needs, rather than adding more bottles to deal with growth spurts etc. then you shouldn't have problems with supply.
It is worth trying some other things to spend more time with your toddler, too - one good idea is to put together a box of things you can do one handed with her snuggling up beside you - books, dvds, colouring, button press type toys, simple board games. This is the feeding box and she can't get it out at other times. The other useful idea is to get hold of a sling you can learn to feed in,which means it's hands free and you're not stuck to the sofa.
Lastly I think it's worth mentioning that at around three months, it's likely you'll experience what feels like a drop in supply. Don't panic! It's normal and just your body adjusting to what your baby needs rather than going by post birth hormones. Your breasts will feel soft and normal between feeds, some women stop leaking, and if you're expressing, output is likely to reduce dramatically. If this happens it's nothing you've done, it's normal, keep feeding through it. It means you've entered the comfortable stage 
Good luck!
To sausage : try latex (brown) teats.