You may be able to buy single quantities at NAPA.
They are called Packard 56 style connectors.
You will need an UNINSULATED style terminal crimper to do the brass terminals
properly. The best deal I have found on a ratcheting terminal crimper for Packard 56 crimps costs about $30.
http://www.ebay.com/itm/1-Cavity-Pac...d717c7&vxp=mtr
http://www.ebay.com/itm/12-Gauge-Pac...8e05d7&vxp=mtr
For top notch quality wire - use marine (tinned) wire. I have used Greg's Marine for years and the wire and color selection have always been first rate.
http://www.ebay.com/itm/14-AWG-Tinne...item51a184be9e