returning to the original question (a low cost back-up carried in the flight bag).
I also have a good experience with a Garmin 60. I choose the monochrome version as the battery life is much longer and didn't consider a colour display a benefit. Cost circa GBP 140.
If not pre-entered; one would have to input the intended waypoints. A little fiddly to enter lat/lon if simultaneously hand flying. However, if ferry flying over the oceans . . .
flyme