Cheapest way to get hashnest code to has for antminer s7.

[sase007]

I was thinking of purchasing a code to hash for hashnest. Can you purchase them directly from bitmain or is it best to go to somewhere like ebay to get them. The Ebay ones look more expensive than the actual hardware, so could be a better idea to purchase directly from hashnest if this is possible.

Thanks in advance for the help!
Sase007