Expansion Backplane, 2 PCIe x4 & 1 PCIe x8 slots (436) - One Stop Systems
PCI Express x4 Flex Riser Card | OnLogic
Amazon.com: BEYIMEI PCI-E Card 4X to USB 3.1 Gen 2 (10 Gbps) Type A+Type C Expansion Card Asmedia Chipset for Windows 7/8/10 Compatible Slot: PCIe x4, PCIe x8, PCIe x16 (Type A+Type