I am curious, it appears that one can get a Minimag AA and a Kroll tailcap (maybe from sandwich shop?) and simply screww the Kroll on. Is that correct?
You might have to fiddle with the rubber switch shroud just a bit. They may seem to be oversized a little but with gentle fingernail pressure pushing the shroud in as you finish screwing in the switch you'll find the switch seats just fine.
14C, if you get a new kroll, the rubber boot would still be tight and hence, it fits the minimag tube perfectly. However, the more you fiddle with the boots and the kroll by removing the boot from the kroll, the more it becomes loose and then you need to press with "gentle fingernail pressure"