Umm, dude, you're in America. Step-down is for us in Europe (220V) to run your (120V) products. Steps 220V down to 120V.
You want a step-up. Well they're available from:
<a href="http://www.radioshack.com" target="_blank">www.radioshack.com</a>
<a href="http://www.mcmelectronics.com" target="_blank">www.mcmelectronics.com</a>
and other good electrical suppliers.
In the UK, step-down is available from:
<a href="http://www.maplin.co.uk" target="_blank">www.maplin.co.uk</a>
<a href="http://www.rswww.co.uk" target="_blank">www.rswww.co.uk</a>
However, if you're using it for AES, don't forget you can just use a US PSU. Check what your PSU gives out (e.g 10V 1.2A, 5V 3A etc) and get a REGULATED one from your local radio shack. Make sure its either AC or DC!!!!
Most consoles will be fine with you doing this - apart from psx saturn etc where the PSU is internal. A lot cheaper than a decent step-down, which is about $50!