This might become less of an issue in the future as more things switch
to standardizing on USB connections, but there's going to be a long time
before that's everywhere. So, for the problem of Device A has a small
barrel plug (female) and the power adapter for Device A going missing
(or the cord breaking), getting a power adapter for Device B with the
same voltage / amperage specs but a different connector working with
Device A: what good options are there?

I've got an audio device (Device A) that needs a very simple 5v 0.5A DC,
and I've got several wall warts that can provide 5v DC 0.5 or more A.
But none of them have a matching co-axial barrel connector.

In the past I've solved this by buying pairs of connectors and replacing
both sides at once. This has worked, but the cord strain-relief I build
is not as good as factory so the cords fail faster. In the present case,
the cosmetics would be pretty bad.

Maybe somebody sells inexpensive assortments of barrel connector to USB
cords? Other ideas?

Elijah
------
used up his stash of old Radio Shack connector pairs