Using a python wheel-only library

Hi I have an odd python package which has it’s wheels not at the URL that’s generated by fetchPypi

{ lib, python3Packages }:
python3Packages.buildPythonPackage rec {
  pname = "opencv-contrib-python-headless";
  version = "";
  format = "wheel";

  src = python3Packages.fetchPypi {
    inherit pname version format;
    sha256 = "";
    python = "cp39";
    abi = "cp39";
    platform = "manylinux2014_x86_64";

This tries to fetch the url, which 404s.

Now normally when I do a pip -v install opencv-contrib-python-headless==, I get a request to first, then it downloads one of those .whl from there. How can I do that with nix?