You can change "MOK".priv/.der to any desired name; "CN=" MUST hold your username, signing the modules may not work otherwise (on shim, possibly due to a bug).
$ openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -out MOK.der -nodes -days 36500 -subj "/CN=John Doe/"