I do it the old style I use the Garmin GPSMAP 78S, that is originaly made for watersport. Very rigid, more than 100% waterproof. Maps from OSM.

But the routing is, well, let's say, a bit tricky. Good to follow tracks you made with another software on your PC.
But no sound, just beeps. Very small screen. If you load very big OSM maps (for example whole Europe) the scrolling of the map is very slow. But if you load just smaller areas (I made a map only for the alps from Munich to Milan) it is fine.

A big advantage is the old round Garmin power connector, this connector is absolutely vibration proof, best power supply you can get. But therefore there is no cradle with integrated power supply available.

I really like that old brick

Ciao
Solitario