I still think your best bet would be a metal workshop to either try:
A. Heating and removing/swapping the spindles
B. Bending the new spindle to match
C. Cut the spindles and weld the old one to the new handle
Or take the gearbox out (take lots of pics for us, Of where and how it fits + the gearbox itself) and we might be able to recommend a modern replacement gearbox that will work with a normal handle.
Actually thinking about it as you never really told us what the problem with the window was it may be the gearbox that needs replacing anyway and not the handle. (try switching this handle with another one elsewhere in the house to work out which is causing the problem).
If wort comes to worst I would recommend going for a "sash jammer" rather than trying to fit a cockspur handle.
A. Heating and removing/swapping the spindles
B. Bending the new spindle to match
C. Cut the spindles and weld the old one to the new handle
Or take the gearbox out (take lots of pics for us, Of where and how it fits + the gearbox itself) and we might be able to recommend a modern replacement gearbox that will work with a normal handle.
Actually thinking about it as you never really told us what the problem with the window was it may be the gearbox that needs replacing anyway and not the handle. (try switching this handle with another one elsewhere in the house to work out which is causing the problem).
If wort comes to worst I would recommend going for a "sash jammer" rather than trying to fit a cockspur handle.