I understand, sorry I don't have a spare 750 wheel.
I know several people on this forum (myself included) have successfully installed other brands of rear wheels on Commandos with great success, both drum & disc brake styles as well.
Perhaps L.A.B. or Jerry can re-name the post, as it would appear you want a 850 MkIII wheel from reading the title...
author "Old Bikes"
too many bikes to list, including:
JPN, 952 Prototype, MkIII Interstate, Combat Dunstall, VR880 SS, Triton