In case bookmarks aren’t your thing, I also stock stickers of some of my designs. They are printed on glossy, waterproof sticker paper (I tested this out, too) with highly strong adhesive. They may be a bit hard to peel off, but once on something, they stay.
I carry some unique stickers that are not entirely made by me and are for charity purposes only. My friend and rep, @thatnerdydragon , designs stickers based off her photography and photo edits for me to put in the shop. Instead of earning a profit, every month or so, we will have a new charity, and the sale of every one of her stickers (minus shipping and production costs) will go to said charity. I will also be making my own stickers based off of my photography, and their proceeds will be donated to charity.
And for those of you with a penchant for creativity or coloring, I offer coloring stickers that work with almost any marker.