What I currently use and works flawlessly. https://shop.louqe.com/products/cobalt-rc260-twinax-gen4-pci-e-4-0-riser-cable

If you like to run the system flipped (GPU down, riser up) then I recommend the following
https://www.amazon.com/gp/product/B09FNY1RLM/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1