Good and cheap do not necessarily come together but I would recommend the new Garmin zūmo® 396 LMT-S (4.3 screen) from Garmin as it is on sale on their website for $299 - $100 off list price!!! Lifetime subscription to map upgrades - 3 times a year on average.
This is an outstanding GPS - check out all this unit has going for it - click to visit site >> GARMIN 396
Comes with lots of capabilities . . .
Comes with hardware setup for bikes but you may need to surf to get the right stuff depending on where you decide to mount the unit but it does comes with a mount. Also you can move the GPS between vehicles and even cars as well with enough accessory brackets.
This unit does do one thing well that many low cost cheap unit cannot do - it has an enhanced screen and can be read in bright sunlight like the BMW NAV VI unit.
Years ago I was a big Garmin 376 fan - this was a marine unit and has a very bright screen and ran automotive maps. Ever since then most of the Garmin motorcycle units including the BMW NAV series could not be read in bright sunlight well that all changed with the NAV VI and this 396 and the most recent zumo units!!
If you get the unit of course:
- download Basecamp - the routing software
- download Garmin Express - firmware and map upgrades
- and make sure you register the unit with Garmin
These are items that may make buying older used GPS less desirable.
While phones do a decent job in my opinion they do not compare with a good Garmin GPS from rugged design and the many capabilities:
-Rugged, glove-friendly, sunlight-readable 4.3” display; resistant to fuel vapors, UV rays and harsh weather
-Stay connected with hands-free calling, smart notifications and easy GPX file sharing for group rides
-Control music and playlists from your smartphone on the zūmo display
-Access free Live Services for traffic and weather using the Smartphone Link app
-Garmin Adventurous Routing™ finds curvy or hilly roads; limits major highways
-Built-in Wi-Fi® for easy map and software updates without a computer
-Helpful rider alerts for upcoming sharp curves, speed cameras and more — plus Automatic Incident Notifications
Just my 2₵
Good luck in your search / decisions . . .