the only Aftermarket cooling i've ever heard of is the HR 03 or something close to it. but anyways its basicly like an aluminum Heatsink for your GPU and you can put fans on it.
who am i kidding you probably know what the HR 03 is....
thats the only think that i can think of that i know thats something like you specified.
as for the housing... like the plastic i doubt you can get one of those.
*edit* Heres a link PC Perspective - Thermalright HR-03 VGA Cooler Review
and if i remember correctly you can put a 120 MM fan on it to help it cool up to 40% better than a standard VGA cooler like what you get on a stock card. swaping a stock for one of these will NOT void the warrenty if your wondering */edit*