I'm not from your area so I can't give you any specific recommendations, but if $ is an issue, have you considered asking your school district to test your ds?
Re people who've had multiple tests - our ds12 has - but he's 2e (gifted + ld).... he's had IQ testing for admission to gifted programs at school, IQ testing as part of the IEP eligibility process at school, and two sets of private testing to understand his disability (both covered by our medical insurance). We didn't start out thinking he'd have all that testing! It's just what can happen sometimes with complicated 2e kiddos.
I hope you're able to find a tester in your area!
ps - we probably are outliers on this line of thought, but our ds hasn't ever been tested by someone who is officially working with gifted kids - and he still has very consistent IQ scores. If you can't find someone who is officially on a gifted-kids website, I wouldn't necessarily discount local testers who screen all levels of kids. But.. that's just me