For SLE 12 SP4 Backports run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:emendonca/SLE_12_SP4_Backports/home:emendonca.repo
zypper refresh
zypper install imagewriter
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:emendonca/15.5/home:emendonca.repo
zypper refresh
zypper install imagewriter
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:emendonca/15.4/home:emendonca.repo
zypper refresh
zypper install imagewriter