The ones that have the two port cable almost always can be used with only one of the cables on the dual end, especially on iMacs. Amazon has a Samsung SE-208AB for $30 shipped. They also have a great return policy if it doesn't work out for you.

Should have asked us first. grin

If you're short on USB ports I got one of these and it's been flawless. You can get it for about $24 shipped on ebay.