"Tomorrow Is Forever" was shown on Turner Classic Movies during their big Welles tribute in May, 2005 and a number of times afterward.
McBride's quote about not being able to locate a print appears in his 1977 book "Orson Welles" from the Illustrated History Of The Movies series (this one focused squarely on Welles' work as an actor). The book was written prior to the advent of home video, so I have the feeling McBride has since seen the film in question.
McBride's new book "What Ever Happened To Orson Welles?: A Portrait of an Independent Career" is scheduled to be published in October.