I wanted a simple cooling fan shroud that would print flat on the bed without supports. I designed this one in TinkerCAD for a Titan Aero. Feel free to modify as needed.
It uses a standard 50mm centrifugal fan like this: https://www.amazon.com/dp/B071WMHNG5
The mount is separate and visible in the pictures See thing: https://www.thingiverse.com/thing:2943038
UPDATE (6/19/18): I modified the fan shroud to have slightly smaller diameter for both the ring and the exhaust ports. I'm getting better air pressure with v2.
UPDATE (3/17/19): I've been using v2 for a while and have been pleased with the results. However, I looked closer at the circular ring and it looks like the interior channel is constricting airflow. Version 3 has a taller ring and an 8th exhaust port. All of the other dimensions are the same.