Target has sleeves for cards, they'd be located where the Pokemon, Baseball and Yugioh TCG/trading cards are. The size might be a tad bigger than the typical PC though because they fit trading cards. I think same with Walmart too. Also they do have plastic card sleeves pages for binders as well, I think they are made of PP and are acid free last I checked. It should say on the packaging. If you are looking online, I recommend the UltraPro site to order from. They also have a store locator function where they will tell you what stores they distributed their products to: https://corp.ultrapro.com/store.php

Just select what country you're from and put in available info, the site will find a local store near you.

Other sites I would recomend are ManduDeco, they are pretty reputable in the K-pop/Tik-Tok community as well and they make sleeves specifically for k-pop pcs, postcards etc.

Or you can order from Amazon, I would recommend this.

I hope this helps.