As twinfan says; Autocom.
I run a Kenwood Funkey PMR unit in combination with an Autocom Pro-M1 control. I also use a handlebar mounted three-position switch. This gives you 'permanent transmit', 'push-to-talk or 'VOX' operation for the PMR.
I have had no problems - the Autocom control unit also accepts a mobile phone, passenger intercom and a CD/Radio as well, so pretty flexible really.
Only down side is the cost.
Cheers, Chris.