Best bet is to begin contacting the primary resource government offices for directories of farms dealing in murray cods.
OTHER STATES
NSW Fisheries
Aquaculture Mangement Branch
Locked Bag 9
Pyrmont. NSW. 2009
Tel. (02) 9566 7842
Fax. (02) 95526627
Primary Industries and resources S.A.
Aquaculture Group
GPO Box 1625
Adelaide. SA. 5001
Tel. (08) 8226 0227
Fax. (08) 8226 0330
Afterwards, it'll just be a matter of calling the farms until you luck out. Good Hunting!