(not necessarily endorsements)

Bakunin - Ethics:The Immorality of the State
http://www.marxists.org/reference/archive/bakunin/works/various/state-im.htm

Bax, E. Belfort - The Ethics of Socialism (and there's more by him on this in MIA)http://www.marxists.org/archive/bax/1889/11/ethics.htm

Dietzgen - Ethics of Social Democracy
http://www.marxists.org/archive/dietzgen/works/1870s/ethics.htm

Lukacs - Tactics and Ethics
http://www.marxists.org/archive/lukacs/works/1919/tactics-ethics.htm

Kautsky - Ethics and the Materialist Conception of History
http://www.marxists.org/archive/kautsky/1906/ethics/index.htm

Wilde, L - Ethical Marxism
http://www.marxists.org/reference/subject/philosophy/works/en/wilde.htm