Where to find a used GPU?

I am looking for a Nvidia GPU, anything above 1050ti 4gb. I have an intel i3 9th gen and will be using the gpu mostly for CUDA and light gaming.

I found a deal for a 1660Ti 6Gb on Famberz Built with 6 month warranty but I think it is a bit overpriced. I tried Facebook marketplace but the GPUs listed cannot pass the 3d Mark GPU stress test.