I've worked in the defense sector and although I have not signed up for one of these gigs, I know plenty of people that have.
It's true that if you are worth your salt (or look good on paper), can obtain a secret clearance and willing to sacrifice a year of your life working 15 hours a day, every day... you can make $250 in a year in Afghanistan.
Good places to look are the company websites: L3, SRI and STG - there are many more. Also job fairs in military towns.
HOWEVER, if you really want to do this, get on while the getting is good. As you may know, the US trying to fold up it's many operations in SWA and other combat theaters, plus while the government is going broke, it's going to be hard for the DoD to justify paying a quarter million a year for each contractor working in these places... knowing what I know from my days in the DoD, I suspect this gravy train will come to screeching halt... and soon.