Just You, Just Me, (Brian Auger), appeared on Rockapella: Rockapella 2; 2000; length 1:49
Have you considered The Swingle Singers, search?
Yesterday from “The Beatles Collection”
"Canon" (NOT Canon in D) JSB Greatest Hits by the Swingle Singers 1963 length 1:53
Conon in D could be the “Acapella Vocal Band” or” Acapella”, both being quite dificult to tag.
I hope this is of some use to you