I'm lucky that I have a buddy who works for a large disposal company. He got a pile of surgical stainless steel mesh that was used as a fish screen in a dam. We made a floor for my roof rack from a sheet of it.

There's a gazillion pill-tablet shaped holes, that are perfect for hooking a bungy's hook onto. For things like my full sized shovel that stay there, I use heavy springs. They don't sun rot, and hold tight. Head for the hardware store to get the size you need.