Not a bad idea. Personally, I'd gamble on the junkyard. You could do your own pressure test (less than 15 psi) to ensure the rad you pull is ok. Junkyards are a massive resource guys - I go there more even often than I go to the strip joint.
I'd go for hotscort's.... now I don't mean to be rude, but if they guy is asking where to find a rad, odds are he's like me, and not too good at working on his own car, so I wouldn't suggest pressure testing and a junk yard, I know I wouldn't know exactly what to take or how to go about testing it. I think what he wants to know is if anyone knows where one can be found at a good price, that will be reliable.