It seems the bubbling is caused by a certain type of sweater (in the crafting community there are some people who can't work with certain types of foam as their sweat reacts with it and turns it yellow, it's genetic luck).
I can't speak for PS5 controllers, but I've done some replacement on PS4 controllers using components from eBay without issue. I don't know if you will be able to find official parts easily. Maybe if you ask nicely at your local games store what parts they use, they can generally do repairs (if you send the controller away). I don't know how much info they can provide. There's a great website called ifixit that has all sorts of repair tutorials for games consoles and accessories so I'd check there too.