http://www.digikey.com/product-search/en?mpart=NSR020A0X43Z&vendor=555
These aren't straight forward to wire and there's no built in safety. These types of boards will happily let you fry them. Don't build under .2, they're regulated but you're still going to have to do Ohm's Law calculations because all these do is essentially regulate output voltage. They're buck chips. You'll need a potentiometer for output voltage regulation, different resistors, a Positive (P-Fet) Channel Mosfet if you want reverse polarity protection, a zener diode if you want low voltage protection. Then you'll need a battery sled, a switch, a 510, wire. There's several tutorials. Digikey has basically everything you need outside of enclosures.
The NAOS 20A Raptor DC-DC regulator board is rated for 120W, 6V and 20A. Remember that, because the board WILL STILL let you output more than 120W and 20A. This is what I meant when I said they'll happily let you fry them. The p-fet and zener diode will add in safety, but you still need to treat the board within its limitations. The OKL T-20 is another 20A chip, but it's a 110W board. There's also a 40A NAOS Raptor that's for higher 3 cell type configurations if you need more power, but there's not many tutorials on it so if you want to go that route I can rig up a diagram for wiring it. You're basically making your own entire regulated mod with these, you save money, but there's more work.
Optional things: heat shrink wrap (protects the board and wires soldered to it from shorts), the P-fet (reverse polarity protection, without it, reverse the batteries and there goes your board), the zener diode (this will prevent you from draining your batteries too low, but it's again still optional), a voltage meter (this will tell you the voltage remaining in your batteries and even the voltage load after sag, these aren't 100% accurate though, what they display depends on how you wire them) and that's about it.
Be fucking careful.