I can now help and yes I make ceramic-coated units. I will be finished with a few designs soon. The cold air portion is the main issue. Anyone can put a filter on the end of a tube. it should be more than a shield. A plastic or steel shield that is not somewhat sealed does not control ambient temp. The cheaper way out that does work is to use a Tupperware or plastic box that fits in the area and then cut it appropriately. It can look good if you add thermal matting or other type of liquid insulation once the unit is made.
Cheap and it will blow away any open cone filter.
I can make you a intake for very little money. Send me a e-mail at email@example.com
and I will send a list of measurements i need. Then I will send you a unit. Yours will be cheap the pipe will be free but shipping and coatings will cost some. Mine uses a ceramic coating. I donít need money up front though so you can pay me later. Drop me a e-mail I will explain.