I believe it still depends on the unit. I carried at one time or another a Gerber BMF, Gerber Aussie Bowie, a kukri, Ka-bar, Buck 119 (6" Bowie), M-9.....I wound up carrying a machete, the Ka-bar, a folding pruning saw, and a Swiss Army Knife (SAK).
I also carried a Gerber boot knife in the small of my back clipped to my belt, never knew it was there and it was surprisingly secure.
I wasn't really in love with the M-9, it was hard to sharpen and has an uncomfortable handle. I really love my Cold Steel ODA, it's not so expensive that you would cry if you lost it (like a Randall, for instance).
At the worst buy the knife of your choice and have it mailed to you after you arrive in theatre.
The biggest risk is your chain of command, as not many people from outside your unit will approach you while you are armed to the hilt with your personal weapon, 15 loaded mags, a few grenades and an AT-4 over your shoulder sitting behing an M-240 and tell you that your knife is too big....