There was a post on here a while back that listed the right model number battery for the tilt-a-mites as well as a suitable replacement capacitor for the original one. I was able to order both from Radioshack maybe two years ago.
I haven't had many reliability problems with the tilt-a-mites and bulbs... Sometimes I get a bad bulb, but they almost always fire. I do have a 3 D-cell Graflex gun to fire the bigger bulbs that can be temperamental, but I think that one got dunked once and probably needs a new firing button.
The biggest problem I've had with tilt-a-mites is people mistaking the big red "test" button for the "fire" button, or not pushing down hard enough on the real fire button. (My slaves trigger by accident all the time, so I never slave my bulbs.)