Thanks to Dan Fromm's suggestion I bought a 12" 1"x1" 80/20 t-slotted extrusion piece from Amazon for $11 (_including shipping _) that has arrived today.
I'm happy to report it works just fine as a rail for my Cambo. There is a slight difference in surface friction so that I sometimes need to help the standard along as I turn the adjustment knob, but no big deal, and it tightens down fine. Of course it doesn't have the spring actuated stops or plastic on the ends, again no big deal.
Actually it didn't cost me anything since I had Amazon points to use. Thanks again Dan!