Silkland 80Gbps DisplayPort Cable 2.1 10FT/3M, [16K@60Hz, 8K@240Hz, 4K@540Hz 360Hz 240Hz] DP 2.1 Cable 16K, DP80 HDR DSC Display Port Cord Compatible DP 1.4 FreeSync G-Sync Gaming Monitor 5090 9070XT

You didn't name what you've already tried but: Silkland makes one which is what I use https://a.co/d/04bXJBvw CableMatters also makes one but I haven't tried it.

Silkland makes a 3M DP80 cable that works well. It’s not certified, but it’s working perfectly for me at full speed. https://a.co/d/022ibFrP