A friend of mine uses an A2515 all the time and loves it. Apparently it was
actually build by Trio-Kenwood. Even though it has Kenwood blood in its
veins, that doesn't take away from its other respectable qualities.

After you've beat the bushes and still cannot find the square plug may I
suggest just paralleling a second jack to the square one somewhere in an
inconspicuous spot on the back and using it instead for your power? The
purists will hate my idea but it becomes somewhat ridiculous after searching
for a long time trying to come up with oddball components.

You should be able to find the manual on the BAMA manual website. If not,
email me. I think I have a copy and would photocopy it. I also think I have
an Allied catalogue with its description which I'd be happy to scan if
you'll email me.

Good luck.