It is well worth having a look at PocketFMS on the internet.
The software is freeware although you can pay a small sum for the enhanced maps.
It has a number of advantages:
It is updated every month and covers the whole of Europe (the rest of the world as well).
There is a very active user forum.
It runs on any iPaq type device so you can upgrade the hardware / software from time to time as tecnology improves. These devices already have very clear colour touch screens.
The package is very small and neat. Very easy to attach to the yolk and if mains power is not available will run for over four hours on rechargeable batteries.
The software can also be installed on your PC and its easy to add routes, and user points as well as change pretty much all the display parameters.