I use my old yellow Etrex GPS when I go biking. It's useful to monitor your trip, speed and elapsed time. But all the systems and cradles I've tried to make for attaching it to the bike (based on plasti ties mainly) were unsatisfactory.
Once, I came across those plastic clips for holding electrical cable tubing and ...I had the inspiration
Step 1: Get materials
You will need:
1) some wood for the base (I used white oak cause I liked the grain an the strenght)
2) four plastic cable mounts ("clips")
3) some screws
4) adesive foam (optional)