I use a 27 cuft steel scuba cylinder and regulator set to 100psi. 100 psi is generally the lowest regs go, but works the best between torque and air efficiency. I use steel cause they are way more durable than aluminum cylinders.
Good for at least 6 sets of wheel changes and air filling. And the best part is that Sport Chalet fills tanks under 30 cuft for free, but you need to have a scuba cert card though. So start scuba diving, it's fun too. Other dive shops will charge either 4 or 5 dollars for a fill.
