There is many toy size / hobby size ones; am looking for something the size of a fist; used in whatever bevel geared mechanism, automotive, gardening, household appliances or any canibalizable from junk yard.  Please suggest what could be a donor to salvage a similar one from.

These are hobby/tool size, images borrowed from the web :

 

Angle grinders have them but I think they would be hard to adapt to anything else. Brushcutters won't be 90 degree... and they too may be hard to adapt.

Many, if not all, automatic transmissions in cars have beveled gears in the differential. Not sure if the size would be right but it should be plenty robust enough for whatever application you want it for.

My Ebay lists 60 pages of them.

17 hours ago, Externet said:

Please suggest what could be a donor to salvage a similar one from.

3D print one..