Operator T-Handle Inquiry

The inside of the window mechanism has the numbers 31512 on the left and the number 40942-A on the right looking outside the window. The crank itself is round inside--no slots to either side. A small screw has to be worked in order to remove the window screen. I want to replace these with a T handle so the crank will not interfere with the new window shade treatments. I have a total of 16 casement windows all with the same mechanism in white.
Thank you!