Very large quantities of Bitmain Antminers you can buy directly from Bitmain after contacting them. The only problem here is that you are need very large quantities and a lot of time cause the order queues are full.
A faster solution is to buy the miners directly from a trusted vendor. There are many online retailers and vendors outsides. We recommend you millionminer.com an online asic miner retailer based in Germany/Europe with a huge selection of bitmain products.
For our visitors we also provide a coupon code for millionminer.com:
With this code you will get an small discount of about 10 USD. We know its not a big discount when you are going to buy some mining machines but if you want to save a bit we recommend you to use the above mentioned code.