When I was in Baghdad (civilian contractor, unarmed
!) I saw a lot of Military Personnel with shoulder holsters. There were a lot of cheapo nylon rigs (bad) and even more leather shoulder rigs.
One of the most common was the Galco Miami Classic. I have three of these myself (obviously I like them!). Only thing is, they are open carrying over there. Horizontal carry means the muzzle is often in someones face. Not really an issue (finger is not on trigger, guard is covered, etc.) but can be unnerving for the wary. I suggest checking with her on any new regs (that were mentioned above), but if it's allowed, it is one of the better, more comfortable solutions and should be readily available from a number of sources (try LA Police Gear and Product Wizard for great prices on Galco rigs). If the discount guys don't have it readily available, try Galco directly. Good Cust. Service and they ship fast if in stock.
ETA: Didn't see ant decent rigs at any of the local vendors at the FOBs or PX's I visited.
Tell your wife we appreciate her service and sacrifice, and to keep her head down and come home safe!