I've been tracking the version search issue on nixpkgs for the last 3 years. Your site is a major win on that front!
I still use Lazamar's tool regularly, so I'm thrilled to see a successor to it.
Devbox (a framework) has the most exhaustive version search for nix that I know of, but it's a bit of a pain because they assume you use devbox to install the package (instead of using nix to install the package)