looking for replacement for Truth window casement operator

The casement operator I need to replace was made by Truth. It is being used on a long, narrow window (10 5/8" x 75 1/2") between two french doors. The operator is about 5" wide and about 2 1/2" deep.
I see the following numbers on the operator:
30471 -- on the rounded hood above the worm drive
306 36 -- on the curved arm attached to the larger gear
30639 R -- on the larger gear
8 3 -- on the gear side of the bottom plate
4 5 -- on the other side of the bottom plate
20544 -- on the straight arm
358-1R -- on the metal plate at the bottom of the door jamb
The U.S. patent number is 4,241,541, Canadian patent number is 350,432. Patents issued 1982.