Finding Riptide weapons

I'm converting a gundam models into a riptide (going great so far). I have a lot of bits for the hull, secondaries, shields, etc. The one thing I don't really have is the main weapons. I'm looking for suggestions on where to get them or good proxies. Any good STLs or is the ghostkeel fusion similar size (I have a ghostkeel I can potentially borrow a part from). I'm eager for any suggestions