I'd try to find a "real" electronics supply store in your area and see if they carry it. Aside from that, you may have better luck buying online.
RadioShack used to be pretty decent for electronics supplies, components, etc..., but lately it seems that they're more interested in selling cell phones than anything else. Heck, most of the time I go in there and ask for something even remotely electrical in nature they give me blank stares, like I just asked where they keep the magical unicorns...