Got heaps of various scroll fans. Filtering and cooling is not an issue. Work chucks out fine filter material all the time down to micron level for some equipment. Moisture can be controlled by a simple drying system. Air flow would be small, there are exit points at the remote/USB connector end that would be sufficient.
Trying to be a bit subtle with this, the camera is still working.
This is for the Canon 1200D, I don't want to open it up .... yet ...
I have thought about the simple fan\heat sink idea for the 450D. Certainly in winter it would do the job over here. Ambient at ~5*.