Check for an RV crash repair shop in your area - they 'should' be able to get the correct seal rubber, pop the old one out, replace the seal then put it back in.
The danger is that they crack the windshield during removal. Once it is out, getting it back in is then easy.
(When I needed to do mine, I had to sign a waiver regarding crack or break - otherwise, they would not do it.)
2001 National Tradewinds 7370 mid-entry DP w/CAT 3126b Diesel
Look for the Mardi Gras 'Gators - Laissez le bon temps roulez - Let the good times roll!!