Your SSD Card is PCIe endpoint? And the FPGA as root port? If yes, I guess you may need to consider to use Cyclone V SOC development kit.
The following link may be helpful to you.
Your SSD card should be an endpoint, which means the FPGA card is the root port, right? If yes, then you need to use a dev kit where it can work as root port (soc board), and has the female PCIe port.
As far as I understand, the device-side is for SSD, so the host side is for FPGA. If yes, which means the FPGA is a root port, then you need an SoC to act as host.