Either a Slime or (cheaper) pick up any cheap motorcar tyre compressor; you can find them in many garages or motorfactors for a few quid.
Carefully remove the outer plastic casing. You will see that the compressor unit itself is quite small. Take out the compressor unit and keep it in a small tupperware box. Job done.
I think you have a 12000GS? If so, it is quite likely that the compressor will draw more than five amps, so tripping the Canbus. Run the compressor off the battery with small croc-clips, which may well come with it. Or you can buy them in Maplin.
Don't forget to put a fuse in line, 7.5 or 10 amp will do.
If you want to pump up an airbed, you will need a cheap adaptor.