Warm and Safe Heated Gear has this versatile adapter.

12V BMW/Car Power Port Adapter for using our 7.4V Heated Gear on Motorcycles, Boats, or in the car in conjunction with the . 

REQUIRED: This adapter cannot be used alone with 7.4V Heat Gear, it outputs 12V and requires the  to safely step down and control heat output for 7.4V Heated Gear.