A couple of years ago, I bought a refurbished Garmin Nuvi 765T
Garmin Link. Model is discontinued but I think you can still get refurbs cheap.
This has a lot of features including:
Multiple point routes - up to 10 different routes
Bluetooth (A2DP stereo)
FM transmitter (to car radio)
MP3 player - most don't have these anymore for some reason
Slot for SD card for routes or tunes
Audio output jack - lots don't have this either
FM Traffic
etc., etc. (see link, above)
This has almost all of the functionality of the newest Zumo's and works with MapSource (or BaseCamp) to download routes from your computer.
I got a RAM cradle and have used it on the bike for over a year.
Downside (with all car-specific GPS) - Not waterproof so carry a plastic bag to cover it or be prepared to wander directionless in the rain. Also, it is difficult to read in bright daylight so sometimes you may have to rely upon spoken instructions (via earphone output jack to earbuds or Bluetooth headset).
Santa brought me a brand new Zumo 665 for Christmas so now I can have all of the features (including XM radio) in a waterproof package. Pricey, but I think I will enjoy it!
Ross