Have been using them for several years as well. I had a 'blue one' Version one, which lasted for years, and just quit working, so I got a couple of yellow ones, which have worked fine. I keep a couple of batteries around, in case I need them, they seem to go out once in a while!
Haven't found a replacement for the TT. Anything that is exposed to the water and is electronic is a little touchy! But it has been faithful little tool!
good luck. let us know how it goes once you get one. they are on sale now and then.
Coach Deb Sagan