I deal with a number of vintage devices, refurbishing and reselling them. One of the annoyances I have is dealing with missing or broken buttons (and knobs, dials, etc.). As silly as it may seem, something like a missing button cap, that has no functional effect on the device, can dramatically lower the value and salability of a device.
Now, if there's an electronic component that's broken, I at least know how to look for it, by its electrical specs or even its model number. However, if I need to replace a button, I'm lost. Buttons rarely have useful identifying markings on them. And there must be thousands of buttons on the market, with many variations on shape, size, physical characteristics, ..., from dozens, maybe even hundreds of manufacturers. At least, so it seems from the searches I've attempted. I've been unsuccessful at finding replacement buttons and such, except in the cases where I had the luxury of the specific manufacturer and part number.
How do you find a replacement button? Are there any tricks to it? Any hints appreciated.