I do quite a bit of bicycle touring and mtb and often have a need for a gps. I didn't want to buy a gps mount firstly because they are quite expensive and secondly they are not so readily available where i live and that means i'd have to order one (which is also quite expensive). So after seeing a bunch of how to's on making one yourself, i decided to have a go.

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 first step was the disassembly of the lamp.
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

After i sanded the inner surface of the lamp casing I inserted it into the PVC bag and glued the PVC bag onto the back part of the housing. I cut and glued the bag so it had a block-like shape.
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

Here's how it looks when finished. It's not very refined, but works for me as i am also able to press the buttons on the gps with ease. The GPS unit fits pretty securely into the mount and doesn't wobble around at all.

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.