Blow Molding Foot Pump

I am working on designing a small baffled foot pump. It is designed to be blow molded out of a soft rubber or plastic. We were planning on molding the pump out of santoprene. However we want to be able to store the pump with all the baffles compressed. We learned that the baffles will not spring back after they are stored compressed for an extended period of time if made from santoprene. What are are some similar materials that will remain elastic over time and can be blow molded?