ORIGINAL: aspeed
I had been thinking of doing some needle valves like the KirnKraft remotes too, but I will likely never find a #2 or 3 x 128tpi tap and button die. I think a 2mm x .25 is pretty good too. If they were a common standard size they are sometimes reasonable, but no one likes to carry stock any more, then they can get a special order price.
I am pretty sure Texas Timers still stock a 128 tpi needle assembly for a TD.
We only carry the regular ones (80 tpi) as the machine tooling is too expensive for a very small run of those. My best advice for someone making their own is to check with a local gunsmith. They would be the most likely to make a custom tap/die in those extra fine thread applications.
Matt