This was about as obvious and straightforward as you could imagine, and the picture more or less says everything, but I'll comment anyway. The original 120V compressor on this adorable little CH rig good for inflating or running an airbrush (really great for that actually, since it's got both a 100 psi cutoff switch and a regulator) broke its piston seal, probably as a result of extended runtime. So I got it at a yard sale for five bucks.
I replaced the compressor with a even less powerful 12V compressor, and replaced the cooling fan with one taken from a PC power supply. The tank already filled through that 1/4 OD copper tubing, which I mangled slightly.