So what's wrong with using a good old fashioned IC socket and stuffing the CPU yourself? Simply supply a few CPUs with rudimentary test code. In fact this could be a positive advantage if you put a bit of effort into the test routines. But with modern ISP chips you may not even need to go this far.

A trick we used to use was scrambling both the data and address lines to the external EPROM. A simple C program did the bit shuffling. Not an insuperable task to trace 'em out and build an adaptor, but an additional layer of work to make a rip-off less worthwhile.