This is an often unappreciated killer feature in Nix. (perhaps not well explained or documented?)

copy runtime requirements:

    nix copy --to s3://some-bucket ./result

copy full build description:

    nix copy --to s3://some-bucket ./result --derivation

copy runtime of the buildtime:

    nix path-info -r nixpkgs#hello --derivation | xargs -n1 nix path-info | nix copy --to s3://some-bucket

Then you set your substituter to s3://some-bucket either in nix.conf or in CLI with --substituters

Or if you don't like s3, point it to https, ssh, or a simple local file directory.