One last idea: gut an RCA connector (either plug or socket, whichever looks most promising). Should be similar then to the lampholder, but stronger.
I tried that the other night, after reading dedmonwakin's RCA thread. Maybe it was the brand of RCA cable, but it wasn't all that feasible IMO (of course, I've only got some basic hand tools available).
This M10 bayonet connector (or maybe the smaller one you mentioned above) might be a better option than even the RCA jack, assuming the petals can be trimmed and shaped to give a solid friction fit against the atomizer threads. The spring-loaded center post for adjustability is an added bonus.