The window manf for
Scamp and
Casita, and prolly many others, is Hehr. Here's one address:
http://www.buccaneermfg.com/
BTW,
Scamp will sell you a rear slider (18x42) for $125 (plus crate & ship, I'm sure) if they are the same. That would be in YankeeBucks, not EhBucks, unfortunately. Scamp's number is 1-800-346-4962 (but the last time I tried to call from EhLand, I was told it was a South of the Border Only 1-800. If any EhLanders can't get thru, I can get the real directory number behind the 1-800.
I dunno what
Casita will do, but it's certainly wise to check.
Pete and Rats