Thats the way I fixed a TomTom Rider (a navigation kit designed for Motorbikes, waterproof and clear screen also in the sun, no loudspeaker, talks with you via a bluetooth unit in your ear or in your helmet, also "understands" your phone for freehand-phoning). With this TomTom, I am able to import my own POIs without problem, I can see them on the screen and I can navigate to them. The mounting unit is RAM, a system from the USA (?) for Motorbikes, so you will find a lot of different stuff to meet your needs. It gets 12 Volts from the car.
4 aircooled cylinders, 7 tires, not waterproof: my m3w Bluebelle (2013) and my 2CV Gundel (1990)