I was thinking the same. ARB makes some too, this model is just over 4′ wide.
http://store.arbusa.com/ARB-Awning-1250-ARB3110A-P3655.aspx
I was also thinking of a hot water system for the other side of the rack:
http://roadshower.com/woo/product/road-shower-4s/
This holds 4 gallons of solar heated pressurized water.
