I found a perfect solution for GPU sagging.My setup is a Coolermaster mastercase and a zotac amp extreme gpu. Even if your setup is different, you might find this helpful to get an idea to solve your problem.I didn't even spend a penny on this and it doesn't look ugly as if you use a support bracket from the market. And the ready made solutions are expensive too. So I think this is the perfect solution for my setup.All you need is the PCI-e slot cover you took off when installing the gpu , a screw and a zip tie.I made a video about ithttps://youtu.be/D5mmSrCG2ok
Hope you find this helpful. Thank you.