I went to my local graphic studio who do vinyl lettering for boats, shops, etc, and asked them to prepare a sign for my tender: 'T.T. yachtname'. They have a special vinyl that is more flexible than the sort used for grp. You apply the sign to your inflated dinghy and leave it for two or three days to ensure perfect bonding with the rubber. After that, you can deflate and inflate au plaisir.
Not much good my giving you the name of the studio, tho': it's in Italy (although having said that, boat name + 3 tender names cost me only some euro 20 which is a whole let less than I've heard for the UK. You could always send clear instructions over and have it posted to you. I'd liaise if you wanted).
I have just painted the name (or t/t ...) on the tubes with boottop, and on the transom as well. I've heard of people painting them very garishly and obviously so as to put off theives. It does need touching up every season (depending on how much time in the sun) but it's cheap, easy - and you can get the kids to do it so it's fun!