These com in handy from time to time in my shop.
Craft Sanding Scraps, 5 Oz Bag, Mixed Grit, Various Shapes & Sizes
They are a bit of a crapshoot as far grit size. These are scraps from maling fingernail files. I have seen the the finger nail files available in grits from 80-12,000. I cost a lot more but you can buy fingernail files in individual grits.