Thread:Mikepha/@comment-24300568-20170630115217/@comment-386913-20170630115536

Japanese Wikipedia does actually list some confirmed names for the suit actors for the two of them if needed:

Black Bison: Hirofumi Ishigaki (also did Chibuchian Butchy; this one at least is sourced by a Hyper Hobby article according to Wiki) Green Sai: Shouji Hachisuka