Soz to but in, but you can use a spare tire for an airsource, I wouldnt advise it personally, mainly due to the thin white powder that may be present inside.
Best to get yourself either a tank of compressed air, kinda like what scuba divers use.
They usually come with a regulator attached and can be hired from gas suppliers and the like. Depending on how much modelling you do, can last many months.
Or purchase a dedicated compressor. I was lucky, got mine for a christmas present (it pays too nag for a whole year sometimes)
I also made an airtank out of an old fire extinguisher, costy only $50.