Epoxy would be the best bet, if you want to try
that method.
I would suggest: get a proper tuning tool, find
a sleeve that fits snugly around the shaft AND
the rotor tip (possibly heat-shrink tubing), then
find another sleeve that fits around the base of
the whole cap, and something to fill the space
between the two, full but not tight.
----------------------- outer sleeve
----- ++++++++ filler
||||_------------------------------ inner sleeve
||||_|------- tuning tool--------------------------knob
|||| ------------------------------
---- ++++++++
------------------------
These are relatively fragile, and will not take
much abuse. Attempts to solder to the post,
while easily done, will undoubtedly ruin the
cap. Plus, the caps are not designed to be
often used - the construction is simple and cheap.
If you can find its ceramic cousin, the whole
top cover rotates, and it is possible to use
it as a grip, although tuning is difficult since
the fingers affect the circuit tuning.
Can you not find a suitable value with the
knob inherent? Small transistor radios might
yield up a usable substitute.
<als>