I'd like to run 2 rain heads, 1 hand shower and a tub spout. I'd like to run the rain heads individually and together. I'd like to do this without an excess of knobs.

Supposedly Omnibrass makes a 5 port diverter, the BV650. That would let me run in 5 modes: 1 rain, 2 rain, 1 & 2 rain, hand shower and tub. Trouble is it's only 1/2" input and I'm concerned about that not providing enough flow for both rain heads.

Yes, running both rain heads simultaneously is required as well as either/or. They need not be able to run simultaneously with the handshower.

Alternatively I could run a Hansgrohe 3 way (4 port) diverter in 3/4" but it would require the tub to be on it's own volume control.

The routing here is supply lines into temp mixer, volume control and then into the diverter. Using a 3 way would put a second volume control off the temp mixer to feed the tub.

So, are there other sources of 5 port diverters?