You can't download a bluetooth dongle, it's an actual piece of hardware that plugs into your computer. You can buy Bluetooth adapters for very cheap on ebay though, although if you're going to buy the bluetooth adapter, might as well buy the USB cord! :)
Are you talking about the part that plugs into the wall is smaller? Apple has decreased the size of the wall-charging part on the iPhones recently to make it smaller and more portable. It could also be a third-party charger. As long as the flat end that goes into the iPhone fits and it plugs...