How about the "hammer-and-sickle" symbol?
For the workers and farmers right? I don't know, seems too similar to the 'hammer and sword' of Nazi Germany.
Didn't the Soviet Union use that symbol during the Civil War, before adopting the fasces after Mussolini's takeover of Italy?
You must be posting from an ATL. In OTL, of course, the attempt to establish Communism in Russia was abortive, but suppose it had succeeded? For a while the Russian Communists combined the Red Flag with the Russian naval ensign and thirteen stars representing the thirteen "soviet republics" to get this flag: