You are right about it being Ian and Sylvia. This was on one of their later albums, Lovin' Sound on MGM 4388. So far as I know, it has not been released on CD, though other songs from the album were on their compilation from the MGM/Ampex/Columbia years, Long Long Time on Vanguard.

I can't promise that I will do it any time soon, but if no one else can come up with it, I will dig it out and listen and at least try to get the words for you.