I was in the same situation a few years ago looking for a low cost GPS. I looked closely at the Chinese GPS units but my research showed a number of problems getting appropriate maps or updating them. I also tried the automotive GPS units (Tom Tom) relying on just the screen for directions. These didn't lend themselves to quick removal/installation and there was always the need to protect the GPS in rain. The cell phone route was tried but again hooking the phone up, making sure it was charged, loss of signal issues, etc etc finally got me to look at the Garmin Zumo or the TomTom Rider motorcycle specific GPS units. I ended up with a Zumo 660 which I picked up brand new at GPS Central for $495 Canadian. Best money I've spent. Easy to install, quick to place on the handlebar mount, self charging, waterproof, bluetooth several ways, fairly large screen, equipped with a car mount for quick conversion between vehicles, etc etc. I've used it for 3 summers with no problems. Great unit.
I realise you are looking for the low cost alternative but I feel you get what you pay for. If you can, wait for a Zumo or TomTom especially when they are bringing in a new model, they often clear out the older units with a big discount.