I'm not a communist, but I come in peace!
I threw this together a few years ago. It utilizes the crossed hammer and ear of wheat used by Communist Hungary during its early days. It conveys the same meaning as the hammer and sickle, while also creating a separate identity.
Also, I disagree about the need to include a taijitu. Communism is a revolutionary ideology, with the aim to wipe away the old order and usher in a new one. The Bolsheviks used emblems that had no connection to old Russia, for example. They wiped away the old emblems with the old order. Including a taijitu in your emblem would run counter to communist ideology.
So here's my suggesting, feel free to adopt it if you wish, if not, no hard feelings.
A more sig-friendly sized flag.