I have a few of the American Harvest (Harvester?) round, stackable tray types. They're pretty flexible. Extra trays and parts are high, as are the tray inserts for more liquid foods.

I have purchased a few for cheap at yard sales in order to have a parts supply and extra trays. One day, I'll also migrate to a box/tray system.

Truth be told, I've used giant homemade trays of wood and food-grade screening for use outdoors or on the porch during the summer (simple air-drying) and that worked well...even with our high humidity.