OK----things are looking up for finding this trim.
Pelland should be on the venders list.
Russ, I was able to find your window trim. It is a rigid screw cover for square windows. Part # H009-351 and is $1.20 a foot, sold in 12 foot lengths, and can be cut down for shipping. There is a $25.00 minimum order on product. Let me know what you would like to do. Thanks, Diana
Pelland Enterprises represents quality after market replacement parts for the RV industry.
800-216-2786 ext 105