My general aviation Sigtronics headset has a mono plug. That stinks, they are super rugged and comfortable.
This thing would have been perfect.
Is it possible to wire the leads from each speaker to a stereo plug, and separate the speakers into stereo?
It is, and it should be easier than growing your own sheep.
The procedure might be relatively easy or not so easy but doable.
The easy one: Unscrew the plug. If there's two different colour wires going to the tip and one (ground, and there may be two of them as well) to the sleeve, then simply get a stereo plug, solder the left channel to the tip and the right to the ring, and of course the ground wire to the sleeve.
The not so easy one: Find the point where the left and right earphone's cables get united and continue as above. The joint would probably be inside the earphone the cable runs from.
Simply put, both earphones have one live and one ground output. For a mono reproduction the live wires have to be spliced together and connected to the tip of the plug. Of course the ground wires must also be coupled, but one grounding point, the sleeve, can serve both channels.