Casement windows crank replacements

I have five wooden casement windows where the worm gear is stripped so that the handle just spins. It sounds like the only option is to replace them.

I have included pictures. The general brand is K K but the only number I could see is-

20810

4 of the windows are the same size, one is smaller.

I looked at your pictures, but was unsure which arm measurements were needed, so I thought I would start here.