I decided to do a vertical mount on the 4090 while I wait for a cablemod cable. I'm not sure I prefer the looks, but hopefully it's less likely to burn up.
Lian Li O11D EVO PCIe 4.0 Riser Vertical GPU Kit - White - Umart.com.au
No BS Vertical GPU Mounting Guide (Pros/Cons & How To) - YouTube
EZDIY-FAB Vertical Graphics Card Holder Bracket Support with Multi-Angle,GPU Mount,Video Card VGA Support Kit with PCIE3.0 Riser Cable- Black : Amazon.com.au: Computers
Ez-40v Graphics Card Vertical Bracket Gpu Holder 5v 3pin Argb Light Graphics Card Mount Support With Pci-e 4.0 X16 Adapter Cable - Pc Hardware Cables & Adapters - AliExpress