Almost all retail RFID tags are on hanging labels, like with the price, or a sticker on the item. Although I did find one inside a pillow once.
A huge number of items at Walmart, Kohls, Target, Academy, Old Navy, and many other stores now (those are just the ones I've seen in store.)
Look for the 'EPC' logo, GS1 is the same standards body that controls the UPC barcode numbering.
https://www.gs1.org/standards/rfid/guidelines
Though - you don't want to use those types for this application, they are too long distance / not selective enough, and the readers are expensive.
Buy a big pack of NFC stickers instead, or print up some QR codes.
> Almost all retail RFID tags are on hanging labels, like with the price, or a sticker on the item. Although I did find one inside a pillow once.
I would say that Decathlon stuff has the RFID inside the internal labels (the ones that you should cut off if you don't want them to scratch your skin but sometimes you don't notice them)