LS-8 parts question (securing tailplane)

(Pardon my ignorance of the proper parts nomenclature ...)

There is a thumb wheel used to secure the tailplane (same for the wing
tips), and a blade screwdriver is used to tighten and loosen the wheel
after the fingers have done what they can.

Yesterday while derigging I made a half turn or so of the wheel before
I noticed the tailplane wasn't moving -- I had forgotten to remove the
gap tape. The tailplane came off properly after removing the gap tape,
but the wheel assembly came out too. It looks like it was secured in
the fin via an "O" ring or "C" clasp. I searched thoroughly for
something that might have popped off but could not find anything.

Does anyone know where I can find a replacement for this missing
piece?

Advance thanks

ted/2N7O