Here's a picture...the window isn't open much, so you don't really see it well, but it'll give you an idea of what they look like. I do think they were an option as I have seen several trailers with the snaps on the window frames. This of course wouldn't work on the frameless Corning Glass windows.
I've not seen window awnings with poles...brackets attached to the trailer yes, but poles no. Doesn't mean they didn't do that, I've just not seen them.
Another idea is window awnings with two corner pockets and some kind of clip or band that holds them in place. I believe there are a couple of folks here on the froums that have made this style.
Shari