I am using a number of official cases until I can come up with something better for multiple Pis.
I used Enzotech 14x14x14 mm copper heatsink on the SoC. I cut a 38mm hole in the lid and mounted the Noctua 40mm fan on top of the lid. I used the supplied cables and pull power from the GPIO pins.
The Noctua isn't silent but it certainly keeps the temps down while its 30+ degrees here in Sydney. I did post a couple of pics here.
They've been running pretty much 24/7 since then (April 2016).