These folks have essentially all you need, possible even the mag. They're great, ship quick and top notch in my books.
Converted mags -
http://natechdev.com/?product_cat=hp...rted-magazines
Fill nipple bit, this is the part you will need to drill and tap into your mag:
http://natechdev.com/?product=quick-...ct-male-nipple
And the regulator:
http://natechdev.com/?product=firebase-air-regulator
All you need is an HPA tank, for that I suggest going to your local paintball shop.