[Eliot Ness]

....There was some sort of rubber sleeve that was on the tuning shaft, that transfered rotation to the tuning cap's gear, which dried and crumbled.

Will need to find a replacement, whether a makeshift solution, a rubber tube piece, or maybe the reproduction is made by someone......

Adams Manufacturing has something listed under under their Specialty Products for A.K. tuner repairs:

http://www.adamsradio.com/

On an A.K. 92 cathedral that I have I found some thick fuel line hose I had that was the right size and used a piece of it.  If that is what you're looking for, then a trip to the local hardware or auto parts store ought to fix you up with a short piece of rubber hose with the right inside/outside diameter.