Welcome to iRV2.
I have to question your RV description .
1988 Sportsman . The only Sportsman I'm aware of wasn't a class A motor home , and if there is an RV Class A , with the Sportsman name , the chassis manufacturer ,( Chevrolet in 88 ) wouldn't have supplied the door or the glass , the RV builder would have .
Could you post a picture of your RV and the door that you require the glass for , maybe we can get you onto the right track for a replacement.