SAS-Expander 4e/8e to 8i/16i

[Stux]

They have separate power connectors and do not need to be in a PCIe slot.

I use the RES2CV360 in my system,

https://www.intel.com/content/www/us/en/products/details/servers/raid/storage-expanders/products.html

Of course, they’re out of production, but available on eBay etc