fork threading is not necessarily 'hard' in my experiences just more of a
'get it right the first time or get a new fork' situation. i have threaded a
few forks and destroyed at least one. after the destroyed one i swore it of
all together but then i ordered a Bob Jackson and it came with a one inch
threadless fork that was just not going to work for the style bike i wanted
to build, so i was back in the game. the shop i work at does offer threading
as a service. i would think most shops that are not bicycle mega stores
would, especially ones that deal with older and vintage bikes. I'm no old
timer in this biz but from what i can tell threading forks was a norm, at
least at my current shop, in decades past. So, call around, someplace is
gonna have the tools, just make sure you speak with the mechanic thats going
to do it before hand to make sure this person knows what they are doing.
Hope that helps.
Josh Shaw