Connectx-8 aux cable

does anyone know where I can find the cable that connects to the rear of the cx8 and then connects into 2 of the MCIO x8 connectors on the motherboard?
I am receiving the cx8 nic soon but need to have it run at 800Gbps. in a pci gen5 server, I need to use this auxiliary cable or kit. Lenovo sells the cable but it is backordered. Nvidia sell as kit but that is backordered as well. Is there a generic cable that might work? ex. MCIO x16 to 2 x MCIO x8. I purchased one of these cables but it looks like the notch in the cx8 end does not line up with the cable.