check the radio shack online - stores sometimes don't have a lot of items... if not at the radio shack, ask them about a store in your area that sells componenets... also, you need to be aware of crimping - some connectors require crimping, but some can be "screwed" onto the cable... or, check ebay, somebody might be selling the wire already... this should not be a showstopper, just a little stumble on the way...

worst case scenario, check digi-key.com, they sell a ton of components...