Compressed air = oxidised and bad tasting beer within 24 hrs.
Soda stream co2 bottles might be your best bet.
Have got "Picinic" setups suitable for you application if your dead keen on carrying kegs around.
getting beer out of a keg is the easy part. Refrigeration is the difficult part. I have a few cold plates in the garage at the moment so just add esky, ice and brine.