I converted my cable park to a USB-C cable (male to male) and lots of adapers (the short sort you can keep in a box) years ago. Yet i have still some devices with a mini-B female port.
Only thing i found online are cables and everything else. Heck, there's even mini-DP > C and ethernet > C in that form factor.
To clarify, i look for something like this but mini-B instead of micro.
edit: Region is Swiss, Europe.
editedit: thanks guys, found one.
Of course those exist, but that does not make them standard compliant. Same goes for power supplies that don't do handshakes. That's not an issue if you exactly know what you need them for, but they're not meant for the general public because you can use them wrong.