Hi Cassfan,
I think the anthology that was the box set that you're looking for is called The Mamas and The Papas: The Complete Anthology. As far as I know, it's still avaliable. Perhaps it's on Amazon. (http://www.amazon.com) However, the 2-cd set released in 2001 called All The Leaves are Brown: The Gloden Era is avaliable, used, from Amazon. Here's a link: http://www.amazon.com/s/ref=nb_sb_ss_i_ ... l+the+leav Hope that helps.
Take care,
Nicole