We do a vox throat mic to work with our PMR446 radio's.
Although it will work with some other too
Have a look on the Icom website
www.icomuk.co.uk
You are lookig for the VS1 and headsets and throat mic to go with it.
I have always found vox a bad idea at sea.
Comunica make a good system using helmates and VHF marine radio's
D S Developments do one, I think, that uses marine band and 446 all linked together
Hope that helps
Regards