“Dongle experts I spoke to told me that the world’s dwindling vintage dongle supply is a real, actual problem that threatens to make vintage computing much more difficult moving forward”.

I had no idea there was such a thing as a dongle expert. :)

Looks easy enough to make your own.

https://lookanotherblog.com/diy-adc-adapter/

I don't see how anyone would make their money back on this. It's way below niche.

This puts me in mind of trying to find one of those dual FireWire/USB > 30 pin cables that Apple sold around the time of the 4th gen iPod. My 4g desperately needs one if I want to sync more than a few hundred tracks, because USB won’t charge it, and I haven’t owned a Mac with a FireWire port since 2011. But man, this things are pricey now, because they just aren’t available anywhere.

I could use a thunderbolt socket, but I’d need a TB3>TB2 adapter first, and Apple want £40 just for that. Then add on a TB2>FW adapter and suddenly I’ve spent twice what I paid for the iPod and the flashmod it’s running…