I just found out about Warner Bros. film archives. Thought I'd check amazon.com for some Debbie Reynolds movies, just to see what's out there, and Mary, Mary has been brought to DVD. I was stunned. A reviewer said
First, a big hurrah for Warner Archive and their order-on-demand video service. Titles that one never expected to see on DVD, many of which have never been on home video at all, are now available from Warner Archive (go to [...] and find 100s of surprising titles, both from the silent and the sound era, mostly at $[...] each).The video was offered on amazon.com through third-party sellers but I thought I'd check the Warner Archive. There she was, for under $20. So check it out and you might be surprised, too!
As for "Mary, Mary," it is a small but definite pleasure to see this unsuccessful film version of a very big Broadway hit (this may have been the first film that was released while the original show was still on Broadway, and it continued to run for some time after the film had disappeared from view).