Step 1: You will need:
A door viewer from the hardware store (mine was 9 €)
A 8cm piece of squishy insulation tube with a hole diameter of around 1.5cm
(This does not need to be a 100% accurate..)
And your camera of course
Step 2: Cutting out the tube:
Make sure to use the zoom to determine the the position at which the lens extends the most.
Measure the diameter of the BASE PART of the lens and how far it extends and use your stanley knife to cut out one side of the tube to fit the base part of the lens. Make sure that you end up with a rather tight fit as this connection will hold the mount.
Also make sure to cut out enough material in the tube to guarantee that the lens does not touch it and can move freely.
Step 3: Almost done!
(you might need cut out some foam here as well.. if your are lucky like me the door viewer fits perfectly.)
Fit your mount to your cam, zoom in all the way in to reduce the black border in your pictures and your done!
Happy fish-eye'in !
hint: Get really close the the stuff you are taking pictures of to get cool stretchy effects.