In order to do anything with air you need to build up some pressure, there are various ways of doing this, one of the simplest is with a compressor.

Standard compressors which are used with pneumatic tools produce up to about 10 Bar and cost about £80+, I am after something cheaper that can produce a higher pressure.
Many years ago I bought a cheap £5 car type inflater, this runs on 12v and can develop a pressure of up to 250psi or 17bar.

The end can easily be cut off and replaced with a 1/4" BSPT to hose adaptor.

What is BSPT you may be saying, I certainly was when I started looking into this stuff.
BSP stands for British Standard Pipe thread and BSPT stands for British Standard Pipe thread Tapered. The BSP fittings are designed to be air tight unlike standard British plumbing fittings which rely on the compression of the copper pipe.

This mini compressor works well although it does have 2 drawbacks, firstly they are slow to build up pressure and secondly they draw about 4-5A, that's 50-60W.

One way to solve the first issue is to use more than one compressor, with this in mind I put together a larger compressor consisting of 4 mini compressors all feeding into a single 1/4" BSP outlet.
I used 3 T junctions coupled together, this gave me 5 connecting points, 4 inputs from the pumps and one output, I connected all the power leads together and mounted them all on a board.