www.gippslandports.vic.gov.au/our-services/berths-and-moorings/Gippsland Ports is the main berth manager in the whole of the G. Lakes system. There is a minor, decrepit marina at Loch Sport, and a East Gippsland Shire council marina in Metung. There are more moorings at Paynesville, run by Gipps Ports and also by the Cruiser Club (north of the Gipps Ports maintenance depot). The P'ville yacht club has fully tenanted moorings.
Otherwise you could anchor in Boxes Creek for a while, or somewhere remote like Newlands Arm or Duck Arm. Or you could find online the newsletter (and paper advertisements) of berths for rent on Raymond Island. Not really legal, as you're only supposed to have a berth if you have land on the island, but not everyone who has land has a boat all the time. Paper advertisements posted on the ferry waiting-room shelters.
Usually also, the 2 supermarkets and the 2 boat shops in Paynesville have paper advertisements on their community noticeboards, for berths or swing moorings, from time to time.