Battelle is great. They also created some software called Cantor Dust [1] that turns files into images to allow humans to easily spot obfuscated data or files.
The sad thing about this kind of work, because I love it, is that to get paid to do it you need clearances and polygraphs and periodic reinvestigations/continuous monitoring and all sorts of things that I find unpleasant.
I'm not sure what you mean but I was a security researcher for a large company for a bit and required none of that. I was required to work airgapped at home, however.
Really? You were doing offensive security work not for a government (/contractor)? What sorts companies, aside from some enterprise pen testers, employ these roles?