As Gunner and Harold both mentioned, rolled threads are superior to cut
threads. Bicycle spokes have very small diameters, and to keep from
"losing metal" at the threaded ends they were very commonly produced by
thread rolling. A good friend of mine owns a bicycle store in town,
and he makes spokes for people with unusual wheel diameters with a
small, hand-operated rolling machine.

One very easy way to find manufacturers and distributors of equipment
and services is The Thomas Register. They were around in paper form
(huge set of books) for many decades; I don't really know when they
started but they long predate my career. The good news is they went on
the internet a few years ago and are free to search at:
http://www.thomasnet.com

Doing a search for "thread rolling machine" produced about twenty
categories, some of the more likely ones a
Machinery: Thread Rolling (126 companies)
Machine Tool Systems For Thread Rolling (6 companies)
Dies: Thread Rolling (155 companies)
Screws: Thread Rolling (138 companies)
Thread Rolling Equipment (21 companies)
Heads: Thread Rolling (7 companies)
Many of these companies will be listed in more than one category, but
it looks like there's quite a few of them out there.

When you start looking at a category, you can see on the left-hand side
a list where you can refine your results either geographically by
state, or (more importantly) by company type. I almost always start
searching with the company type set to "Manufacturer", because they
usually have more complete product literature and the application folks
can answer real questions. If the manufacturer has a website, and most
do now, the site will be listed on the information page.

OK, just for fun, a few unusual searches typed in at random:
"Gold Rivets" 30 companies, 24 of them manufacturers
"Brewery Vats" 7 companies, all manufacturers
"Concrete Pumps" 125 companies, 63 manufacturers

Sorry for the long post. I've used Thomas Register for over 25 years
and always found them to be complete and quite accurate. I'd really be
kind of lost without it. I just thought I'd mention their existance.

Dave