eBay, theres probably plenty of cheaper, used ones that are in good condition up for auction. Just make sure you ask whatever auction you're looking at that the seller has a good rating.
i got my kids one each from hmv.plus you get a loyalty card ,which when you spend a certain amount you get points,which are redeemed against your next purchase or you can keep saving them,i think its a 1000 points =£5.00 here check em out [Only Registered Members May View Links| Click here to register]