There is info on the ST Mini insulators here
Kanger replacement Subtank insulators
FT sells RTA insulators. Maybe they have one that will fit.
I haven't experienced any RTA deaths. My original Kayfun lite's are fine. I don't see those dying ever. They'll very likely outlive me. They're built like battleships (borrowed from Bronze). I think any decent RTA if maintained will be fine.
You can still buy the RBA deck for the STM. I have a couple STM's and extra RBA decks in my stash. They are decent atty's.