Well thank you for the advice Steven, therefore I will need to try it myself, ordering a thumb tip online semms risky to me, it might not match my skin color or something like that.Hey Umbelino,
To be honest with you any thumb tip will do, find one that's comfortable, matches the color, texture and size of your thumb and work on your handling and you won't have any problems. The Vernet TT's are pretty good and don't cost a lot of money, you may have to try a few different kinds and find which suits you. In the end the most important thing is to learn how to use it properly, not necessarily which type you buy.
S°
The only saving grace is that they're pretty cheap, so if nothing else you can order a whole pile of them for less than $50 and try them on til you find the right one.