[Boatanchors] Mystery Clark headset plug question

[Ken Kaplan]

I have a David Clark H7041 headset that has a special plug. It looks 
like a short 1/4 plug but it is actually .280 in diameter and 3/4 inch 
long. It has 4 contacts (2 for the mic & 2 for the phones). A guy in my 
local pilots shop said it is used in helicopters but I got the headset 
from a shop that works on fire trucks. I think it was used on either 
their radio or intercom (or both). The pilot shop had an adapter that 
converted it to a pair of standard 1/4 stereo plugs for $56! A picture 
of the plug is here:

http://www.qsl.net/kb7rgg/radio/images/plug.jpg

Anyone know where I can get a socket for this plug?

73 Ken kb7rgg