gpg --no-options --no-default-keyring  --keyring /usr/share/keyrings/debian-keyring.gpg --export --export-options export-minimal --armor --output path/to/put/it.asc keyidhere

Types: deb
URIs: http://people.debian.org/~josch/debian
Suites: ./
Signed-By:
 -----BEGIN PGP PUBLIC KEY BLOCK-----
 ...