No clue. Maybe you should do a search for heat-stamping information. I think I'm going to do one...I'd like to know what can/can't be heat stamped. I just realized that I've never been asked if I'd like something stamped and the one time I did (on a Keepall) I was told it could not be done anywhere but on the address tag!
I believe some stores will do bags, while some will only do wallets or luggage tags. My boutique will only do luggage tags unfortunately. I've heard though that sometimes they've messed up on the bags, which is why very few boutiques (if any) will do them anymore.