The switch is from a Chicago Electric SDS Rotary Hammer, model 69274. It's a fairly ubiquitous trigger switch, not terribly robust from my inspection compared with better-brand momentary switches, and likely used in many inexpensive power tools.
I learned that the switch body on these things (the black bit in my photo) conforms to a common form factor and is used a lot of tools, regardless of brand/make/model/price point, so finding a switch body to replace that which broke in my tool was not my problem. The trigger is the issue.
Turns out, triggers (the orange bit in my photo) are spec'd to conform to the contours of whatever tool they're going into. The trigger means of attachment varies as well; e.g., post, slot, keyed. Additionally, triggers are commonly sonically welded to that means of attachment, so swapping switch triggers between switches bodies--which was my intent--is improbable.
I never did find that FD04-2116. I ended up using a new trigger switch that kinda kit, and now completely fits (with a little modification). My tool is back in service; and I now know way more about these particular 'momentary ON detent switches' than I ever expected to.
