ikea bag hack from funk station, greg of daddytypes was inspired to create a diaper bag complete with changing pad out of a single big blue ikea shopping bag.
you'll need to unpick the seams of the bag first. turn the top portion into a narrow tote bag and sew the two identical leftover pieces together as a changing pad.
if the changing pad is a little too thin for your liking, add a padding layer to it.
see greg's diaper bag and changing pad flickr instructions.