Similarly - I was recently looking for a replacement pivot for my mountain bike, and found a machine shop in Whistler, BC (arguably the current Mecca of mountain biking) that specializes in making upgrades for parts that regularly fail in current models, as well as specialized accessories.
Yeah! For photography there is SK Grimes who does the same kind of thing - they're really a make-to-order machinery shop who just happens to be involved in photography stuff. They have both "standard" stuff they do all the time, but if you have some novel idea that you really need manufactured, they'll do a one-off for you.
I think specialist components for niche hobbies is a great niche generally - especially when the hobby has the potential to blow up into something bigger.
Bikepacking bags (and to some extent ultra-light hiking) are good examples that come to mind where people started things as hobby businesses in their garage and they quickly expanded because of demand.
https://pinnermachineshop.com/