Indeed - most rims that you'll find listed as being 26" are probably mt bike rims and would be unlikely to fit a road bike made for 650's.

650's are not too hard to find - some shops even carry them in stock. I just went today to have new wheels built for my commuter and was pleasantly surprised to find they had rims there. I'm getting Mavics. I've had Sun Rims and Velocitys (which I do not recommend for anything more than easy duty/dry riding - they disintegrate under less than optimal conditions...)

If you don't mind ordering your wheels you'll find a wider selection.