Itaewon is crap anyway. Overpriced lady drinks that get you nowhere and they whip your ass playing pool.
Outfcalls to the hotels are expensive (tourist prices)and decent hotels sometimes give you grief. The best bet IMHO is any shop with an illuminated barber pole (red, white and blue). Also girls often put business cards on the windscreens of cars to advertise, grab one or two and call.
The worst that can happen is getting 2 or 3 hair cuts in one night.