Your best bets are either
Radio Shack, which is a chain of small electronics/computer stores that have branches on every fricking corner here in L.A. including one almost on the airport property itself, CompUSA, which a chain of slightly larger computer stores but doesn't have one particularly close to the airport, or, your best bet,
Fry's , a chain of huge computer superstores that does just happen to have one of its 5 areas stores
really close to L.A.X. If you can't find it there, you can't find it anywhere.
Edited, Mapquest was giving wrong directions