Looking at the photo, any porch awning you have will have to go down the rear windows.
Failing that, here's an idea. Buy a proper full size awning, but get one that is too small for your van. You can convert full awnings into porch awnings with a kit off ebay where you cut the beading to allow it to come out, and then add a leg and padding to bring the awning down the side of the van.
If you do this at the front, so the awning fits properly into the channel at the back, but finishes before the front window.............. job done!
Does that makes sense?