I understand. Standard industry practice has reasons, some to do with efficiency, standing behind their work and and of course making as much money as possible "without actually cheating".The rim strip that I bought is 29 mm across. But it is designed for a dirt bike so that should be fine.
I've been told by tire shops that for safety sake they always replace both the rim strip and the tube when they replace the tire. It's just standard practice. Doesn't mean anything's wrong with the old tube though.
Some shops are plane incompetent and dishonest. I had taken the car in to have a head gasket replaced. When I got the car back, it overheated before I got home. He then changed the radiator as well as the water pump. He installed the oil dip stick sleeve backward. When he put the hood down, it broke the sleeve where it joined the engine block. He then glued it with two part epoxy. The car still over heated, there was smell of fuel in the radiator and the dip stick was glued to the sleeve (with the epoxy). Now, it sounds funny. Total bill was about $3000 in 2002. I took the car to the dealer who told me the head gasket was blown, which the shop claimed to have replaced. I reversed charges with the credit card company. The shop complained, the credit card asked me for evidence. I submitted dealer's statement. I got my money back but then the shop went to small claims court. Every one told me it was open and shut case and that I would win. The owner of the shop worked in my company where I worked about 1200 miles from home. I was an out of towner, so to speak. The judge listened to the shop owner for 45 minutes and gave me less than 5 minutes to explain the case and ruled against me. I gave up at this point.