For those who might want to 3D print there own (the print a temporary one while shapeways prints a nylon one), you can get the file from here:
https://www.thingiverse.com/thing:4234854
Sorry I didn't get this out sooner....
Also, any feedback from folks who've already installed one?
I'm happy to iterate over the design a bit and improve it where needed.
Thanks!
Ian.