I have built power supplies for Sotas using a 24v regulated power supply. 1 amp is plenty. there are lots of these for sale on ebay. Some even come with meters and variable output. Simple.
Or really, any wall wart 24vdc power supply will work if it puts out at least 800 ma.
Or really, any wall wart 24vdc power supply will work if it puts out at least 800 ma.