If you know any truck drivers, see if they can get some of those airbags that are placed between certain freight items.
I used to work for a paper converting site. We would get rolls from the mills and often times they would place those heavy airbags between the rolls to prevent movement in transit.
Opened up and filled with plastic, they lasted for years, much longer than the U stuff it covers. By the way, I'm talking about the airbags that are woven plastic or vinyl not the paper ones.