I found this place with an appropriate extruded heat sink material. It is about the right width for the controller base and has a 5/16" thick base so it will be plenty strong enough to mount in any manner you choose and strong enough to anchor an enclosure to.
Extrusion Profiles
They sell it by the foot so it would be perfect for the 11" long controller.
You can even get it black anodized.
A simple aluminum box "lid" could be mounted to it on a hinge to allow you to access the internal components easily.
Filling the end panels of the top box with 1/4" to 1/2" of potting material or silicone would make them safer to work with.