Hey there,
Thanks for writing in! The operator you have is an older style Roto Operator which is no longer available, unfortunately. The only replacement we have for it is the 39-248 Roto Operator Base.
That said, one of our senior experts has personally installed the 39-365 9-1/2" Single Arm Operators, used along with the 39-504 SS 13-3/4" Channel Guide (track), in its place. The opposite handed version is the 39-366. To install them, in addition to removing the existing operator and its compatible hardware, you'll also need to make a few adaptations.
When our senior expert installed this operator, he had to make the opening that the operator fits into about 1/2" wider and taller to accommodate the newer operator. You'll also need to drill new holes on the bottom of the swinging window sash to install the channel guide. This part of the repairs will be a little tricky but it is doable.
We do advise exercising caution when drilling so that you do not drill too far into the frame, possibly damaging the glass.