Historian writes about fitness implements; provides cool history, but ignores the present, as the author knows little about modern fitness (you need go no further than his last line for proof).

Clubs and maces are still extremely popular today- they are just not part of the "standard" fitness tools of:

1) Weight machines
2) Dumbbells and Barbells
3) Treadmill or Elliptical machine
4) Mirror for which to gaze upon oneself

While only kettlebells have managed to- temporarily- add a fifth to that list, the more "traditional" or "historical" elements of physical conditioning- maces, clubs, medicine balls, rings, axes/sledgehammers, sandbags, kegs, kettlebells and stall bars (along with their more modern descendants, the rower, the conditioning sled, fan bike, tires, and load-bearing vest) have never really gone away, instead finding a permanent place in "legitimate" training, away from the commercially-driven bodybuilding gyms, aerobics studios, and running clubs. They experienced a partial public resurgence with Crossfit, which made them easy to acquire in the mainstream, driving down their prices from "specialist goods that cost an assload" to "I can buy these from Rogue Fitness for a fraction of what they were two decades ago", but they have never really gone away- you just had to be serious enough about human performance to know where to find them.

Find a serious gym devoted to strength & conditioning, and you will find inevitably find all of these implements, and maces and clubs especially. Louis Simmons at Westside Barbell in Ohio- long considered the pre-eminent powerlifting gym on the planet- released an instructional Indian club and mace video almost twenty years ago. A serious devotee of physical health and conditioning might even consider the inclusion of these items to be a "litmus test" of sorts to determine the seriousness of the facility's ownership to accommodating your fitness goals.

A quick addendum: Page 2 of Kehoe's "Indian Club Exercise" book includes a diagram of a rowing machine. Several times, the devotees of Indian Clubs are referred to as "gymnasts", which undoubtedly means they had spent considerably time making use of, at the very least, stall bars are rings, and likely also medicine balls and bags for carrying and throwing, which were en vogue during Victorian physical conditioning fads.