I decided to design an alternative Daughter plate for the Modular Carriage for TEVO Black Widow designed by Elzariant (you can find it here https://www.thingiverse.com/thing:1829292)
The original design was Elzariant (which I give to all the credits for the design of both the system and the daughter plate), I modified the original to fit a blower (I tried several duct and several axial fan, but I find lack of pressure every time) and I added a duct system for cooling the parts. Now it has a decent air flow and it seems to work well. I liked also to have the design the as compact as possible, so I came up with this thing.
There are two version:
one has a closed duct which blows all aroud the nozzle.
the second is opened on one side (it looks more like a "C") so it lets you mount easily your extruder.
I printed it in PETG 100% infill 0,4 mm nozzle 2 wall thickness