I can't really answer the question asked, but I can say a few things.
AFAICT, most printer mechanics work directly or indirectly for the manufacturers and their business partners, and independent ones are a bit few and far between. I think this is because, unlike say cars, almost all printers are owned by entities who get the printers on service contracts, and there's not a consumer market. (Or to put a finer point on it, there are plenty of consumer-level printers, but these are generally poorly made, short-lived, and impossible to repair, so they're not advisable if you're starting your own distro or publishing project.) So the mechanics are employed in relation to the service contracts, and rarely in independent shops.
If you buy new, or lease, then you pay more, but it's relatively easy to get support at a reasonable price or even free (you already paid for it) and reasonably easily. And in this case, you don't really need a list of mechanics because you're probably under a service contract or something similar.
If you instead buy used, then it becomes pretty hard, and expensive, to get a mechanic. We've always bought used (we were never happy with the cost of leasing, even when we factored in the perks), and sometimes this has cost us a lot of stress and tears and sweat. But we've never really felt the need to bring in a mechanic (except when we had offset or risograph printers, but I think that's out of the scope of your question?). We've instead used a combination of:
- The manuals and repair guides published by the manufacturer
- The replacement parts available on ebay etc
- Online printer repair forums
- Deciding when to let the printer die
Because we've gone DIY on the repairs, and downtime on the printers has been so painful, we've long ago decided to always have (at least) 2 printers, so that we can keep one running if the other is down for repair.
Long story short, whether you buy used vs buy new (or lease), ends up having big consequences. Some on here will say getting printers on a service contract was the best decision they ever made. I'm still very far from being convinced it's worth the price. YMMV.
I think the same will probably go for binders. Within the support window, the manufacturer or vendor will support you pretty well, but as time passes you quickly end up more on your own.