Looks like you can get it directly from buy for $38.24+ Free Shipping
http://www.buy.com/prod/xbox-360-color-accessory-pack-wireless-controller-with-new-d-pad-play/217184182.html
I did exactly what you said using this case.
http://www.amazon.com/Hard-Disk-Drive-Case-Enclosure-Included/dp/B004YV9TSA/ref=sr_1_1?ie=UTF8&qid=1330545164&sr=8-1