How big an air compressor

Be very careful about selecting a compressor. On initial startup of compressor amperage levels can be well above the running amperage. In the specs on link this Honda 1000 has max amperage at 1000 but run is only 900 Watts. Honda EU1000I

About a 1000w compressor.

amps times volts = watts

Multipy the known amps times 120 to get watts.

Amps times voltage gives Watts.
Should be able to run something like this:
Compressor