maybe something like this?
http://www.bikesdirect.com/products/...y/avenue_c.htm
a Sora rear derailleur is plenty for a beginner, and it's always fairly easy to find a used Shimano 105 rear derailleur for a good price on ebay if you felt the need to upgrade. they don't offer up to 60cm, but have a sizing guide that might help. do you have any cycling gear? if not then you'll need to budget for that as well.