What i used:
- an old bicycle lamp housing which was just the right size and fit for my old Garmin eTrex
- a PVC transparent bag (i found an old swissair toilet bag)
- a set of pliers for cutting the plastic, X-acto knife
- a screwdriver for opening the lamp casing
- sandpaper, super glue, scissors,
- velcro strips
Step 1: The Lamp Housing
The half of the lamp casing that attached to the handlebar mount had some plastic brackets for the batteries and screws so i had to trim that down with the pliers and X-acto knife.
I than sanded it a bit for a smooth surface.
It's a good idea to wear some safety glasses for this stage as the plastic tends to fly around as you're cutting it.
Step 2: The PVC Bag
I did this with the gps inserted into the casing so that the fit was just right.
I then trimmed the PVC bag a bit for a slimmer look and added the Velcro strips.
I used super glue (loctite super attack) for binding everything together and while the PVC-PVC bond is very strong, the PVC- plastic bond is a little weaker but still seems to hold just fine.
Step 3: The Finished Product
The PVC should also be waterproof to a degree.
I have yet to test it thoroughly but the first impressions are good, it stays put even if i shake it around pretty wildly, so I'm optimistic.