I use an ex-RAF mk4A (with both boom and mask "hooks") when appropriate, I think it cost me £200 about 10 years ago. I've replaced the microphones with D-C electrets (a bit of a pain in the mask, but do-able) and added a variable resistor to each of the ear cups, but you could keep it standard and have an external adapter box.
Whatever you end-up with, make sure there's a weak link or pigtail connector if there's any possibility of getting out in a hurry - it would be awfully sad to be connected to a terminally-broken aeroplane by the helmet cable.
Someone suggested the D-C shell that takes a standard headset - IMHO these are pretty poor compared to the mil helmets. The soft ones are quite good though if you just want to hold something on during neg g.
HFD