PCIe slot bifurcation

[Phishfry]

I wondered what kind of bifurcation devices you are using.

I have just purchased two dumb cards for an NVMe Array.
Unicaca ANU22PE08
These are not widely sold but seem to fit the bill. Two NVMe from one x8 slot.

I had previously bought an x16 card for 4 NVMe's
iOi Host Adapter

My first bifurcation experience was with the Supermicro SLG3-2M2

What have you used?
Where can I find risers for x8 lanes to 4 each x1 lanes?