What about using a car gps? I use a garmin nuvi, an old one too and I can add any number of addresses as way points. Pick your final destination, add waypoints along the route you wish to take. You can save a bunch of routes, and can search routes, pick backroads, highways what have you. I picked up a waterproof cover for mine, and a marine grade cigarette lighter plug on ebay or Amazon. The plug is a simple 2 wire setup with an inline fuse, glass style, and mounts on your handlebar or frame. I'm sure you could mount it anywhere you wanted though. The gps mount came with a handle bar mount but it was cheap. I ended up getting a cup holder from gander mountain with a bar mount, suction cup mount, and Velcro strap that I can screw the waterproof cover onto. That gives you a ton of options on mounting within easy view while riding.
A little hard to hear it talking if your bike is loud but its a plainly visible route on screen.
Hope that helps. Any questions on what I picked up to fo this or where I got them feel free to ask