Here's an adapter I made to connect any headset with a boom mic to fit my FT-817. Finally, with the VOX on, I can row my boat or hike a mountain trail totally hands-free as I 'work the world' on ham radio. The schematic came from the files on the FT817 Yahoo group site.

Closeup showing the three jacks. The outer two are for headsets with separate "mic" and "earphone" plugs. The center one is for single plug types. The buttons control PTT, UP, DOWN and FAST functions, just like the stock microphone.