Would it sound dumb if I said "sand"? Clean sand will stick to double sided adhesive or a wet adhesive like Elmers (sample attached has sand stuck on with Glossy Accents). A child's play sand pit or a bag of builder's sand are not usually hard to find and you only need a spoonful. Just make sure it's dry before you work with it (I put mine on a bit of foil and put it in the oven for a while).
Otherwise I'd have said the same as Holly - a coarse sandpaper, maybe with a torn edge.