The store.
I'm sorry, I had to. People are being too helpful and I had nothing useful to add.
LOL! Testify Brother!
Really, ANY place that sells to the local Machine Shops, is going to be able to provide what you need, as long as you are capable of telling them what you need. "I need taps for Gun Threads" is not that.
If you need a #6-48 tap, be prepared to tell them whether you need a Starting, Plug, or Bottoming version, or the full set. And order High-rock taps if dealing with high Rockwell hardness levels on the work.
If you need to get weird, like as not, they have a custom tool maker that can supply you with a 13/64ths diameter, .3mm pitch tap, if you really need one.
FWIW, I dealt with Thomas Skinner and Sons, in Edmonton, a lot, and got no few custom tools through them (usually grinds of oddball radii on end mills), so I know they dealt in custom order stuff a fair bit. There were, and probably still are, a couple CNC tool grinder outfits in the Edmonton-Calgary areas.