BK, I have a video of a live 1982 TV concert called "That's Singing: The Best of Broadway" (according to the video box, the original title was "Showstoppers: The Best of Broadway"). Anyway, it has Alexis Smith singing "Could I Leave You?" from Follies. Is that something you could use?

Should point out that the tape is not the complete version of the show that aired on PBS. I think I still have it.
There were many performances by the originally stars singing their songs. Many in semblances of costumes and set pieces.
Here is what's on the tape.
1. Everything's Coming Up Roses--Ethel Merman (Gypsy)
2. Quadrille--the American Dance Machine (Can-Can)
3. Get Some Cash for Your Trash--Nell Carter (Ain't Misbehaving)
4. You Could Drive a Person Crazy--Donna McKechnie, Pamela Myers, Susan Browning (Company)
5. You Made Me Love You--Debbie Reynolds (Irene)
6. Try to Remember--Jerry Orbach (The Fantastics)
7. Shriner's Dance--Chita Rivera and the American Dance Machine (Bye Bye Birdie)
8. Summer Loving--Barry Bostwick and Carol Demas (Grease)
9. Sleeping Bee--Diahann Carroll (House of Flowers)
10. Never Will I Marry--Anthony Perkins (Greenwillow)
11. All for the Best--Stephen Nathan and David Haskell (Godspell)
12. Mean to Me--Nell Carter (Ain't Misbehaving)
13. I Believe in You--Robert Morse (How to Succeed in Business Without Really Trying)
14. Could I Leave You--Alexis Smith (Follies)
15. Charlie's Place--Donna McKechnie, Wayne Cilento, and the American Dance Machine (Over Here)
16. Little Old New York--Chita Rivera and the American Dance Machine (Tenderloin)
17. Pretty Woman--Len Cariou (Sweeney Todd)
18. Send in the Clowns--Glynis Johns and Len Cariou (A Little Night Music)
19. Those Were the Good Old Days--Ray Walston (Damn Yankees)
20. They Say It's Wonderful--Ethel Merman (Annie Get Your Gun)
21. Lullaby of Broadway--Jerry Orbach and the entire company
In the Broadcast was:
Mary Martin and children (Ethnically mixed) singing Do Re Mi
Debbie Reynolds Alice Blue Gown (I think) from Irene
I think Tom Bosley did something from Fiorello as he was the host of the show.
I believe other performances were also dropped from the original broadcast.