After spending lots more time looking at wheels on US ebay, I found this candidate. The rim size is 16 x 3 and is aluminium, which will allow a 130/140 wide tyre. The down-side is that its going to cost around $225 to get it landed here (from Texas) and I still have to buy a brake plate & brake shoes. It also uses a 17mm axle, the same as the DR. Its from a Kawasaki KZ650CSR which appears to be a US only model. I really like the square profile-deep rim.