AFAIK, it's not going to be perfect - there are other less likely reactions alongside every aneutronic one, and there is no ways to stop them. So it would be like 10% of the flux rather than zero.
Well, the reaction of Helium 3 with itself produces two protons, one helium-4 atom and a lot of gamma rays. Only the gamma Rays would really be capable of producing new neutrons, the charged particles could be kept in the plasma and separated from the fuel by their different charge to mass ratio.
The problem is: We would need to harvest 2 billion tons of lunar soil every year, just to produce enough Helium-3 to allow producing enough power just for the USA. At perfect efficiency.
Wouldn't work, we would need a better source for it. Or a different reaction with more chance of neutron production...
Did somebody already investigate if the strong neutron reaction of a fusion reactor could be used for burning nuclear waste? Like putting tiles of nuclear waste into the reactor chamber and let them absorb neutrons, while cooling them (and produce more energy from the absorbers?)