First, thanks to The Winger, wh actually picked up an adapter for me at a FUTURE SHOP in Montreal on his way to YUL on Friday afternoon. We spoke as he passed through YYZ.
I had used the RADIO SHACK Canada link he supplied and as I noted on Friday afternoon, finally got it to accept an order for two of the adaptors. This morning Purolator delivered a rather large box containing a pair of rather tiny OMEGA Aircraft Headphone Adapters [item 3378001]. Cost was $5.98 each plus taxes, but no handling/delivery charge [unless I wanted Express service].
Not bad service on both accounts. Thank you again, The Winger. I am sure you can make use of the extra one, but should I manage to lose both, I know who to contact.

And thanks to KH and AW, and others who assisted in the search.
Irony or ironies, after this continent-wide search for the darn things, I find OMEGA is located in Downsview!
Anyhow, gotta love this here little community of ours...