Join Date: Oct 2014
Location: Greater San Diego area
Bikes: Downtube Mini 2015 version
Try a hunter's backpack (especially a bowhunting one), like the Exo-Mountain Gear (my brother-in-law uses this one). It has a compressible space for the bike and a limited backpack. There are many others in varying sizes by several makers, but this should do the trick for hauling, collapsing (but NOT fold away). None of them are cheap, but they will last a lifetime.
If you just want a carrier, you can get what they call a meat hauler, which is just a frame with straps. Of course it does not collapse, but you can get varying sizes (some quite small and some fold down). Kuiu makes a very light frame with straps, so it takes almost no space.