Amazon says hello.
Classic gaming, at least from a hardware perspective, is a pretty big business. If you can't find an adapter for your controller, you can almost always find somebody who built one in an afternoon from ten dollars worth of parts.
As far as special keys on emulated systems, it's very rare that they aren't provided for. This specifically talks about the Commodore 64 emulators available and how they provide for special Commodore keys.
The lesson here? For every one of us that has two pieces of old hardware sitting in a crate in the corner, there's some crazy guy still writing software for it, another crazy guy building hardware for it, and a third writing an emulator or driver for a modern system/OS.
"Conversion, fastidious Goddess, loves blood better than brick, and feasts most subtly on the human will." -- Virginia Woolf, "Mrs. Dalloway"