NIXPKGS_ALLOW_INSECURE=1 nix-shell -p nodejs_16 -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-23.05.tar.gz works for me with cache.
Node.js 16 is EOL as you noticed, we provided during the 23.05 release cycle cache for this insecure package, by now, it’s highly recommended to move away from it.
I recommend to stick with release rather than exact revisions if you don’t know exactly what they contains.