I use to use a Garmin 500 but it died and now I upgraded to a 520, the 520 does a lot more mapping but is still smaller than the 820 or 1000. I have not used the mapping on the 520 yet but the two nice features are that it shows text alerts when paired to your phone (Bluetooth) and it has a simple user replaceable battery. Technically the 500s battery needs to be replace at the factory, you can replace it yourself but it takes fairly major surgery. The wife (stoker) uses a 810 and runs the maps since she is the navigator.

Cheaper options might be to use your phone with a phone mount on the bars or something like the Wahoo RFKT that mirrors the ap running on the phone. I elected not to go in this direction over concerns that the phone battery would be an issue on longer 6+ hour days.