The testers who work with gifted children are definitely your best bet. However, I had to find free testing for our daughters who are homeschooled.
I called our local universities until I tracked down a program that does IQ testing for free, working with doctoral students. In addition, one of our daughters had some neurological issues, so it turned out that her WISC testing would be covered through our insurance.
This may be a risky strategy and it definitely is not advisable for folks who can afford private testing with people who are experienced with testing gifted children.
