I had a 78 Argosy with those same front windows. I have heard they are available from Airstream but only come in a solar grey tint, your originals are clear. You could possibly find one n.o.s. ( new old stock) somewhere or get one from a salvage unit but the chances of that are slim. Forget about Lexan, those windows have a compound curve which cannot be replicated with a flat piece of material. I know because to tint them you must use section the film into three pieces. Some of us Argosy owners were debating on the possibilities of breaking one some months ago, too bad for you but now we know it can be done.