Hi, Skipjack.
I think that you can get the signal via an AUX out on your mixer (as usually done for the monitors) and feed a headphone preamplifier (Behringer makes at least two models) which powers an in-ear monitor (a lot of stuff on the market, Sennheiser, Shure etc.)
Not the cheapest solutions, but it works...
ciao
Ghirotondo