Maybe I'm not understanding correctly (which is common now that I'm considered "elderly") but why do you need the entire window?
Is the frame damaged?
If the frame is not damaged and intact, a good auto glass shop that offers RV services should be able to custom cut a piece of replacement glass and fit it into your frame. Or so I assume as I've had that done years ago at a local glass shop where I was at.
Have you called an auto glass shop in your area? If not (and the frame is in good shape):
Try Zenith Glass as they have a good reputation there in Duluth and I've head good things about them from others as I have several journal entries on RVers getting various types of glass work done there and being very satisfied with the work and cost.
Zenith Auto Glass -----> website go HERE
3802 Trinity Rd
(from that webpage linked above)
RV Side Glass Repair
Is the side glass broken or leaking on your RV or motorhome? Our technicians can repair or replace the glass on any make, model, and year. Whether you need windshield replacement, rear glass replacement, or side window replacement, we’ll take care of it so you can get back out on the open road faster.