Cost me all of $2.00 and a couple of hours of my time.
Went to the local Bunnings (hardware store) and picked up a 75mm round down pipe. This fits very snugly around the zoom ring on the Tokina and doesn't need any extra padding on the inside. It also tapers slightly so you can push it in and will stay snug. Longest part of making this was cutting off the flange with a hacksaw.
To make up the required diameter to reach the zoom gear on the housing I used a combination of some flexible magnets and those rubber bands people wear around their wrists.
The rubber grips the housing's zoom gear quite well and at the telephoto end once you reach the limit it won't turn further unless you really crank it but it does slip on the wide end when you reach it. I might try and find a toothed belt that will fit around it or may use velcro or have a go at making a tooth rack from polymorph.
Edited by Jesper64, 31 July 2011 - 05:42 AM.