You can get filled at most welding supply shops, or soda/bar distributors. It's about $15 to fill and will fill about 20 tires from 20-40 psi, probably 12+ from empty.
The bracket can be mounted anywhere you want, some do it in the back seat under the seat, some do in the bed, mine is on my rack.
Shown here, on the left side:
The bottle pressure runs between 500-800 psi! Nothing else is needed. My setup came with the bottle, bracket, filling hose, and regulator.
---------- Post added at 08:03 PM ---------- Previous post was at 08:01 PM ----------
Here is the setup I have:
POWERTANK - CO2 Air Systems
It's not cheap, but it's by far the highest quality portable CO2 system on the market. A company called "Outback Air" also makes a system that is much cheaper, just not as many bells and whistles.