Still, the site can still be used as a reference source.One example, below, is the Tamiya Gearbox housing. I discovered that it is actually identical for most of the major models, with the exception of the Panzer IV. This means that any box can be adapted to fit other models in the list below, so long as the correct driveshaft are fitted, and the correct standoffs used. In some instances, (given that the shaft is only held in by a circlip, and can be removed in seconds) anyone with a bit of milling skill could even adapt a driveshaft to fit another model.
Here's the housing:
- Tamiya Gearbox Housing- Jagdpanther
Here's the portal into the pages of Tamiya treasures in stock there.
https://www.modellbau-seidel.de/index.p ... zteile.web
It's a pity that individual driveshafts are not listed here, along with their part numbers. Maybe I missed them.
No one would want to throw a perfectly usable gearbox unit away, just because of damage to the driveshaft- and so, it must be possible to obtain them somewhere.
At least with part numbers- provided by this site- (for myriad other sprues and bits), it's easier to begin a trawl of the 'net. 
They're not currently available on Axel's inventory...