There's a FB group called "Vintage FAI" free flight, owned by Abbotsford BC's Nigel Tarvin, who is near me and I have met. They have discussed the Max III .15 some and it was recently posted that the spraybar is (only) 3mm OD.
That makes it smaller than the FP .20 parts and right around 1/8" OD....measure the holes in the case to confirm that. I would guess that a .10FP spraybar/NV would fit, perhaps a .15FP, or there might be an Enya part that would work. I might ask Randy Smith if he has the parts you need...you never know!
FWIW, I'd make an offer on your Max III .15, if it's a good runner, in good shape, and you are considering selling it. There will locally be a special event for "Cranfield 10" designs from 1960 WC...ten competitors were declared "Joint Champions" in 1960, after all the prescribed flyoff rounds were complete and everybody maxed out. Pretty historic!

Steve