Does your friend have a budget amount in mind? Does he want a finished car, small project or large project? Does he want the R model colors of white with blue stripes or is he open to other Shelby colors? Does he want a dead nuts copy or a loose/individualized interpretation of the actual R-model?
Check out the NorCal Shelby club website as well as the SF Bay Area Craigslist. There were a couple or a few listed in various states of completion.
www.norcal-saac.org
http://sfbay.craigslist.org/
Also, try
www.collectorcartraderonline.com. They usually have several listed too.