Garmin makes a number of handlebar mountable cycling GPS devices. All their motocycle GPS devices have handlebar mounts including many of their Etrex line. There are GPS mounts on ebay for your cell phone if you like.

I like to create my own route so there's no need to even see the street level. Once your route is created, all you have to do is have the GPS run in "Arrow" mode to point you to all the turns. People think you need this expensive large GPS or tablet on your handlebar and that is not the case. Learn to create routes on your computer then upload to the GPS.

I've been using a GPS for years and never purchased the maps until several years ago. I did fine uploading the route and just following the "Arrow" which is large enough to see even with a small GPS.