http://cgi.ebay.com/WWII-18-Wood-Ste...item4cf88b2212
It says it is 18" diameter, cast spokes and hub, says it suits CMP, CCKW, DUKW, G508 and G506. I didn't think all of these used the same steering wheel, but perhaps the seller just means it will fit.
Given the $400 buy it now, I don't think the reserve will be at a level I'm interested in paying. (OK, you can call me cheap if you want.)