I am looking for rolls of sticky backed vinyl with some design or other on the front.

I did see them for sale in Festival on a pop-up stand last year but now can not find anyone selling the stuff. Can't find it in HomePro or other DIY type places.

Anyone know of a shop in Chiang Mai which has any?

I want to use it to stick on some doors to 'beautify' them, so need it to be at least 45cm wide and 2metre long. I've seem it on Ali Express but suspect I'll get done for taxes if I order from there, anyway difficult to see what the design is from their pictures.

Never seen this but if it exist then best to try the shop halfway Nawarat Bridge and (main) post office, same side. They sell budget carpet, vinyl, neoprene, foam for sofa cushion, rubber etc. etc. Best in town for this.

Edit: if you mean normal adhesive plastic, I think opposite the 7 Eleven on the corner at Kadluang. (rolls with plastic table cover outside)

Stationery shops will be best for this product , it was invented for covering schoolbooks. All sorts of designs and patterns.

Lots of it but not sure about patterns. Shop on Tippanet Road, East side, across from the government bank.