Use LiteX on the Acorn CLE 215 · enjoy-digital/litex Wiki · GitHub
Amazon.com: Mini PCI-E to PCI-E Express 1X Extension Cord Adapter Card with USB Riser Card : Electronics
Clearance!Tiergrade Superspeed 7 Ports PCI-E to USB 3.0 Expansion Card with 15-Pin SATA Power Connector - PCI Express(PCIe) Expansion Card USB Card for Desktop PC Support Windows 10/8.1/8/7/XP - Walmart.com
P21S-P21F (Flexible x1 PCI Express Extender)
Is there a Mini PCIe card edge footprint available? - Footprints - KiCad.info Forums