fan duct for Geeetech Prusa i3

I was looking for a fan duct for my Geeetech Prusa i3 and found lots of them, but didn't really like any of those, because they weren't designed like I design my things.

I would have liked to edit existing designs, but noone would upload step-files. I want to do that so you can work with the CAD program you like..

The last picture shows why it's not a good idea to use the type of fan - the gap leaks a lot of air! A radial fan would have been better, but I used parts that came with the Geee