window crank

Hello,

We have some windows that open with a crank 3 of them are no longer functioning properly so I need some parts. Where the handle attaches, some of the little ridges are damaged. And I am missing one crank handle as well. This part of the hardware seems to be the main issue, but hard to tell without being able to crank open the window.

Would you be able to help me find the right part? The long arm of the window opener is 12" and the short one is just under 7". The length of the box with the crank on it is 5". I couldn't find any brand name or other identifying marks. House is 1957, but windows are more recent than that, if older.

Thank you!
Phaedra