Unfortunately, the only "480W" units that come to mind are PSU-shaped objects offered by companies like Logisys. Good for no more than half their claimed ratings, they are also missing protection circuits, so they have a tendency to take attached parts with them into the fiery abyss.
If you absolutely must go cheap, a Corsair CX-450 or CX-550 (but NOT the CX-500) would suffice, and are typically inexpensive (<$50, sometimes <$30 if you play the rebate game and win).