ClearAdhesive Vinyl Sheets DIY Stickers 4"x4.5" 200+ Sheets Sticky Back Upcycle New, old stock. The backing is a little yellowed but the vinyl is totally clear. These came from a screen printing shop. The owner used to print decals and stickers. They are repositionable, not permanent when put on a shiny surface. After they have been there long-term, they may not be repositionable. You can turn them into stickers by putting any paper or thin material under them and then cutting to size. Or they can be printed on if you use the right paint / ink.
eBay