PCIe 4.0 X4 /X8 to X16 Riser Card Converter/X16PCI-E Gen 4 Extension Adapter New | eBay
PCIEX16D03 | PCIe x16 to two PCIe x8 Slots Expansion Board | GPU Docking | GPUs Docking
Expansion Backplane, One PCIe x8 3.0 slot (440) - One Stop Systems
PCIEX16E-844S | PCIe x16 edge connector to one PCIe x8 and two PCIe x4 Slots riser cable | x16 to x8 and x4 PCIe bifurcation riser cable | PCIEX16E-844S
P27F Series (x16/x8/x4/x1) Flexible x16 PCI Express Extender
MAIWO M.2 expansion card KT058A NVMe SSD to PCIe 3.0 X16/X8/X4 adapter M Key Converter Card Support 2230 2242 2260 2280,Compatible with Windows 7/8/10 & Linux ,BTC accessories - Newegg.com
ONE STOP SYSTEMS PCIe 3.0 x8 Dual-Port OSS-PCIE-HIB38-X8-DUAL