I've bought windows and other items from this seller (Vintek RV) on ebay. Good seller and safely packaged and shipped the items. I also bought lots of trim from this seller at a good price and $259 with free shipping for these doors is one of the best prices I've seen. I actually bought two of these exact doors from a different seller for $250 each including shipping, and one arrived a little banged up because of poor packaging. So I would hope Vintek RV would do a better job making the small price difference worth it.
My only concern is these are the doors Little Guy uses on their trailers and nearly every demo model I've looked over the glass had separated from plastic piece you use to push the window up and down. I think this piece also has the little spring loaded tabs that hold the window at a certain height. Maybe people were just being too rough with them, but for the price you'd think they would be made a little better. They're easy to install though and waterproof.
Or try Lil' Bear:
http://www.lilbear.teardrops.net/parts7.html#doors
Lucas