The sites
@Tonkaman listed are good, some other suppliers to check with similar brands and options are:
Newark.com
Jameco.com
Digi-Key.com
Alliedelectronics.com
Mouser.com
I used to price shop these along with the ones previously mentioned almost weekly. At the time I was looking for the best deals for an engineering firm I worked at in college. Sometimes they can be within a few cents for the same item, and other times over $100 difference for specially crimp tools. All of them are good to check for pins, connectors, switches, etc. It's also worth noting that buying individual pins on a cut ribbon can be significantly cheaper per pin in bulk than buying them individually, if you are willing to clip them apart. The other upside is you don't have a bottle or pile of individual pins to spoil every where while working.
Eficonnection.com has a lot of the connector shells and pins for LS Swap harness items as well.