For what it's worth you could also use an off the shelf switching power supply like these:
which range in price from $3-$35 from various sellers on the auction site in voltages or 5 to 24 VDC and current ratings of 1 Amp to 50 Amps.
You could also pull a power supply form any old desk top computer made in the last 30 years for a nice 15-30 amp 3.3,5, and 12 VDC power supply.
JGL