If you are looking for entry doors like what is shown in the picture, I just ordered one last fall from Challenger door. E-mail Jason Helmuth:
JRHelmuth@challengerdoor.com
He is very friendly and will get you setup. My French door was around $450 and freight was another $125. It was custom made to the size I wanted and all you have to do is bolt the frame in. I have also ordered storage compartment doors from them and they are pretty reasonable as well in the $50 to $100 range. I haven't ordered any single entry doors from them yet but I know they make them. If you are in the Elkhart area you can just pick them up and save some shipping money. The best place I have found to buy windows and single entry doors would be Bontragers Surplus Inc. They have anything and every thing you need. Windows have an incredible selection, around $50 each. Have to order trim rings for the fight wall thickness but those are readily available. Their entry doors are around $125. They also have lots of lights. Amazon also has lots of RV lights for sale.
Steve