You could do an internet search "Fan Shrouds". You should get a lot of hits on sites for different manufacturers and for vehicles.

There was an article in one of the hot rod publications recently on fabbing your own from fiber glass or metal (tin, aluminum, etc.) You can also purchase them from some retailers made of ABS plastic. You have to cut the hole for your application. I think I have seen them in Southern Rods and Parts ads. If you are using an electric fan you could always buy the Cooling Components fan/shroud unit to replace what you have now. They run about $225.