In reply to highaltitudebarista:
For the Caldera Clones, I've used large foil roasting trays from 99p Store.
For a JetBoil windshield, a flapjack tray, or sidewall of a beer can, as suggested above, tucked under the neoprene sleeve. Ready-to-cook lumps of meat often come in very sturdy foil trays, too; probably the thickest recycled food containers I can think of.
Just don't block much more than a third of the vents...