Need a PCI-Express to PCI adapter for a 1U server. Preferably with a flex cable like this, but only need the one PCI slot:
Either that or maybe something like a 45-degree adapter, but I've never seen one of those.
Here's one here. "1-slot PCIe x1 to PCI-32 bridge-based active riser card for 1U chassis"
Your server vendor may have something appropriate as well. You may have issues mounting non-vendor risers in a 1U server, although with a fixed right-angle adapter it will at least retain some stability due to being mounted in a slot.
I've had custom flexi adapters (although not with bridge chips) made by Adexelec in the past. Very happy with the results.