Your example from Amazon looks perfectly adequate except for the 2' length. I'm not sure why you think it's incorrect.
Radio Shack lists several as expected, including 6100410 which is 6' long and white, but since their website sucks and no one in the store knows anything about anything including the power cords plugged in to all the equipment on their sales counter, they're a poor source unless you know more than you seem to about the matter.
Best Buy has this:
http://www.bestbuy.com/site/c2g-15f...1310042261.p?id=mp1310042261&skuId=1310042261
and probably others. Weirdly, most of their cords are "hospital grade". To their credit, they have meaningful product descriptions such as "NEMA 5-15P to IEC-320-C13" which is what you want.
Target may not have anything unless it's listed as an accessory part for a printer, computer or TV and the staff will be as knowledgeable as the Radio Shack staff.
You actually might have some success at a Walmart, Lowes or Home Depot. They undoubtedly list them online and the larger stores will probably have them in the computer or electrical departments.
I'll remind you that thrift stores usually have a big pile of these very cheap and I have a vorpal sword so don't wiffle at me.
