Been there, done that. Fairly recently too, like this past summer.
You have to use tempered glass. My experience, my local glass shops dont like doing custom cutting tempered glass work.
I did find a one man company that only does commercial glass work. He helped me out and got me tempered glass custom cut to my size and corner radius, I have frameless windows, for a fraction of the price. It was just the glass. I still needed to figure out how to adhere the hinge and emergency latch to the glass like the factory does.
My jayco dealer got me a complete window ordered and had no idea on when it would be in. Ended up taking a couple of months.
However, I did a TON of sniffing around the ole interweb and found a place in Elkhart, IN. My window is an LCI brand window. This company showed this particular window only for a Keystone brand. Whatever. I learned windows are windows. Just like tires for vehicles, if it's a X brand tire in a Z size, it dont matter if it came on a Ford truck from the factory, itll fit a GM truck or a Ram truck if it has the same size tires on it.
The windows are sold by the size of the hole in the wall it fits into. Measurements dont have to be EXACT, if they are off by say 1/4" here or there, it'll fit.
Unfortunately you'll end up having to buy the complete window, frame and all. If it's a frameless window, itll slide right in the original frame.
Here ya go;
https://elkrv.com/
Dont have a heart attack when you see the prices, but they are still a bit cheaper than the dealer and much faster getting the needed window to you also.
I ordered mine late on a friday afternoon and it showed up Wednesday.
Good luck and keep us posted!