I designed an air duct for use with open air cases that can be 3d printed. It will mount to a 120mm fan and sit the BCU inside of it. This should work for VCUs as well but the power header on the vcus is facing the top not the back so it wouldn't be ideal.

STL File: https://ufile.io/12bsr
OBJ Files: https://ufile.io/j58do