Steve
Not sure on the size of this nursery,anyway your best bet maybe in acquiring used ginseng shade cloth. Surfin,sould help find what will fit your need. As for structural supports, used ware house racks work good, just paint them black, you can find them in bankrupt factory sales. There's a few of them around lately due to you southener's greed...L.O.L...?. I'd use the 80% shade cloth not the 75.
Guy