Actually they aren't specifically for 'molex' plugs, I've found the same plugs in quite a few varying plugs in different things. In fact, if the truth be known, the plugs probably aren't even correctly termed 'molex' as molex is the company that probably started making those plugs.
Much like vacuuming is commonly known as luxing or hoovering (depending on what part of the world you are in) due to the manufacturer of the appliance...
the ones in drive power connectors are .093 pins and the ones in ATX connectors and such are square and are called MiniFit Jr They can be purchaced cheap at www.digikey.com PM me for order numbers