Promag and ATI both have collapsible stock systems "in the works," but I doubt we'll see either product shipping before the holiday season rolls around.
That said, the Promag system looks promising, at sub-$200, it basically clones the Benelli collapsible stock, and includes a forend that has left, right, and underside Picatinny rails. I'm hopeful that I can get my hands on one.