I get mine from Amazon from a brand called Baskiss. They are thick pvc sleeves and I have used them for about two years now. They aren’t super big sleeves so they can fit normal pcs but if it’s a pc that’s about the size of a Pokémon card it would not fit. Hope this helps!
Also not a ton of personal experience but there's a lot of youtube videos for record collectors on the topic, they are SERIOUS about it. When I was researching turntables, I got a ton of videos about vinyl storage, I'd suggest starting there.
Sorry I don’t have personal experience with sleeves but in general don’t leave it near areas where it could be damaged more. Don’t leave in direct sunlight or under direct light, and don’t leave it near window or close to ground. I’d reccomend leaving it behind glass and avoid touching it if you want the best quality and least fading. This is coming from my museum work experience lol