The expander includes side walls positionable against a bag interior, members articularly connected together and to the side walls, and an arcuate enabling diamond shaped mechanism connected between the members and the side walls to provide a selected expanding and contracting amongst the members and the side walls. The members are in a folded condition when the bag is compressed and, with the aid of an expansion motivator such as a rubber band, spring and the like, the bag is expanded to its deployed condition.