I usually make new ones or fix the ones I have. The problem I have with buying a new USB cable is that they're just selling you copper with plastic on it. It's nothing special or crazy in there, it's literally 4 copper wires running end-to-end. If you're technically inclined, I'm sure there's a WalMart near by that sells cheap USB cables.
As for the wire and end cap connectors, I usually get them off amazon or if I'm in the city, I go to Fry's if I don't have spares to Frankenstein.