How to get latest Cargo version

latest version of Cargo even in unstable is at 1.72.1.

1.73 has been out for a while now. Is there any way to get the latest version?

It appears the update to 1.73 has been merged in nixpkgs

This is done with overlays, as mentioned in the wiki.

Check out either fenix or rust-overlay.

They both provide a way of having different Rust toolchains, for example, the latest stable one or nightly.