I was doing some more research yesterday... I have a technical/mechanical brain that don't let me leave good enough alone (a curse) and found out that the Maskuni does have a 3/4 thread, but it is a 3/4" PT (according to California Bonsai website) while my brain thinks they are just some metric size... probably M22 (but don't know the pitch) as most water pressure washers. What I did find out in a Japanese website is that they advertise the Masakuni rosette as a replacement for the Kikuwa (which is identical to the Joshua Roth). And if that is so means that it could be swapped... I think you mentioned it before, but the liquid PTFE will probably do the trick to stopping the small leak.
@Jeramiah, can you spec out the Masakuni to see if there is a possibility to offer it on your website? For those of you that don't know Jeramiah's prices are pretty spot on with the Japanese prices. I was looking at buying the small Masakuni M9 (no relation to the Beretta M9) wire cutters and while everybody else had it up-charged, his price was around the same price on the Japanese website.