Years ago before the non skid plasitc came out I bought them from Joannes' I think. They are just little sandpaper dots with adhesive on them. Work great. You could just use regular sandpaper, cut out your dots and glue them on somehow.[/quote]
You can also buy thin sandpaper with an adhesive back at most hardware stores, easier than gluing.
My Joanns still sells the sandpaper dots. I find them more effective than the clear plastic ones