Picked up a cheap computer power supply and printed a lid with some holes for switches, an indicator light, and 4 binding posts. 3.3v,5v, 12v for under $20. And plenty of amperage. In hindsight, wished I had put a USB charging port on it while I could. The piece was a 6 hour print, so doubt I will re-do with the port.

I included the 123D design file so you can move your screw holes as needed.

Printed lid. Cut all the wires I didn't need, keeping black, green, yellow, red, and orange (3 each, 1 green). Green and black to switch, yellow and black to 12v indicator light, orange, 3.3v post, red, 5v post, yellow, 12v post. Wires all three wires to each post for max current carrying capacity, then jumpered black and yellow to switch and light.