Thanks! The platform I'm using is voog.
There are pros and cons - their pricing is better than etsy, but the process of adding products and the backend is not as streamlined.
While not THE best, but a quick fix for cheap, see below. Use them for extra space in my storage area (spare bedroom). Akro has been around for quite a while, really like their products. Also great for Lego!
https://www.amazon.com/Akro-Mils-10724-24-Drawer-Plastic-Hardware/dp/B00012FQEM?ref\_=ast\_sto\_dp
I'd say to just get a binder. If she has separate individual stickers like you'd get on redbubble, trading card (think Pokémon card) sleeves like these would work well. If they're individual sheets, standard clear binder sleeves should do just fine. :)