L'antre Du Dingo checks out the recently released ETU from Perun Airsoft designed for the Tokyo Marui P90.  It is also compatible with other Tokyo Marui P90 clones such as the ACMs, Asia Tactical, Classic Army, Cybergun, CYMA, J Tactical, and JG. It is incompatible with G&G and Krytac P90s perhaps due to their having their ETUs/MOSFETs.