I found mine in a local newspaper ad. Sellers, of course, want 20-100% more than an old Corvette in need of restoration is worth. Be patient with them. If you are interested in their car, and the price is high, call them a few weeks after their ad runs out , and make a reasonable offer. If they say no - wait a few weeks and try again.
Local auto shows usually have car collectors of all types. A lot of them have old Corvettes in storage, or know someone who does. They are usually looking for garage space and money for their current project car.
Whatever you do, check the FRAME very carefully. Nothing is more expensive than having to pull the frame out from under a car to work on it - unless it is a legal fee - for a title to an insurance company contested car (check web sites and your state police to validate the VIN before buying).