Here's a starter list of web sites that sell Ben Hur canvas tops. if you buy one, or have one, please post your feedback. Quality, fit, price, etc.
List is in no particular order:
http://www.canvasco.com/gmc.htm - Seems to have a full line of canvas for the CCKW. Lowest price depending on exchange rate UK
http://www.newlifecanvas.com/8422/10769.html - A few positive comments, mid range price, lots of CCKW canvas, USA
http://www.milweb.net/go/alliedforces/ - No web site, e-mail address in add. Seems higher priced. UK
https://www.beachwoodcanvas.com/ - Lots of canvas for CCKW, high prices. USA
http://www.odcloth.com/products.html - Not sure if they do trailers, not a lot of CCKW canvas. USA