CUI has released an extra tiny 3W power supply series. It's essentially 1 cubic inch. It'a also a little bit cheaper. The one big change is that CUI recommends an inrush limiting resistor on the AC side, which should help protect the fuses from wear. This will only work for the Hydra, unfortunately, and not for OpenEVSE II. 3 watts isn't quite enough headroom to drive a 12 volt relay (which is something OE2 still supports). But the Hydra exclusively supports contactors, so 600 mA @ 5V is plenty.