Thank you for the interesting ideas and clown pictures but this is actually a real costume that I am trying to build and I'm actually looking for somebody to help me build the circuit board for pay.
So the power is planned to come from an 18V (not 12 V as I previously said) lithium ion battery pack that I have. It is is DeWalt DCB 203, vmax 20 volt 2 amp hour battery, actual voltage is 18 volts. The 18 volts can go directly to the compressor which takes an 18 volt input and draws a lot of current. The compressor is actually a Ryobi OnePlus handheld pool toy inflator. Then the power supply would also supply two bubble guns, they are made by bubble storm and they draw 4.5 volts, and four leds, these are the micropuck kits from LED supply and they draw three volts. each LED has its own controller.
It would be helpful have a single circuit board that I can mount on the inside of the costume. The circuit board would step the 18 volts down to 3 volts and 4.5 volts. Both of these are low power draw, and I do not anticipate having to dissipate much heat. The circuit board could be bolted to an interior carbon fiber surface inside the headdress of the costume.
To make it easy to assemble the costume, ideally the circuit board has wire connectors to the load side, for 18 volts, for the 3 volts, and to the 4.5 volts, so that I can take the battery out and recharge it, or connect or reconnect the other parts as I put the costume together for the final performance