12 Volt compressors are available anywhere auto or RV parts are
sold, at prices from about $10. The cheapie units tend to be very
noisy, but do the job. One with a built-in gauge is preferable.
I have been using an "Inter" brand compressor for about 20 years.
Great little unit - but I think they are out of business. I put a
long "truck type" chuck on mine that allows me to reach the valve
stems of a 182 with wheel pants (but without the little doors).
It's a pain in the rear, but doable. If it's hard to move the plane
with the tires low, jack it up - one side at a time - then turn the
wheel until the valve stem is accessible Push the tail down for the
nose gear (takes two people).

For those with small 110 Volt compressors, Costco has been selling
1 KW inverters for about $69 lately.