I suppose it depends on what you want to spend; dealers like Peter Loy and Aperture tend to deal only with equipment in good condition and consequently is slightly more expensive than other dealers or Ebay. However, this extra cost is often offset as you don't have to pay out for a CLA.

Another Idea is to go to Photographica where you will be able to play with a number of Barnacks. Here's a link to a thread about it. I know that Peter Loy intends to be there because I asked him.