The RepRap Wallace is a fairly recent design. You will have to make it yourself with the aid of the RepRap Buyers' Guide and the Wallace Build Manual.
If you have access to a 3d printer, the printed parts design files are available through http://www.thingiverse.com/thing:14208 and https://github.com/whosawhatsis/RepRap-Wallace
Folks who have printed a Wallace for sale
- 2PrintBeta - All parts needed to build a wallace available, with casted parts.