My xbox 360 is broken!!! :( i got all my downloadable games on it!!!!?

all the game stores near me only sells the new xbox 360 Slim, and it's not compatible with my current old xbox 360 hard drive!!! all my games is in that hard drive! I don't have access to a credit card so I can't buy old phat xbox 360 on ebay.. I don't want to pay again for all the games that I've downloaded..