The A11 is a state of the art, just released SoC. I thought I had read that it has >4B transistors. I highly doubt that there is anything available anywhere (just for kicks, I checked Aliexpress). You do realize that all recent Apple SoC are paired with other major components on the logic board, such as the NAND, BaseBand etc. That means even if you did find a knock-off, it wouldn't work on any iPhone logic board.
Perhaps you can explain why this is of interest, there might be some other help we can offer.