PCS LM2596 Buck DC-DC Adjustable Step Down Power Supply Module Converter:

http://www.amazon.com/Retailstore-LM2596-Adjustable-Supply-Converter/dp/B009HPB1OI/

 

Ferrite: Pot Core - (ICH) B65943A-X22 Pic 47 mm 29.8 mm

http://www.surplussales.com/Inductors/FerPotC/FerPotC-1.html