I made one using duct work sheet metal. A friend of mine cut the metal to my specs and punched two holes in each of the four sides near the bottom for air. I used a piano hinge with pop rivets to connect the 4 sides. Bent some metal rod I had lying about for the folding handles. The grate on the inside was cut from an old BBQ grate I had. Drilled two holes for tow of the grate pieces to fit and a pop riveted lip on the opposite side to hold the rack up. I'll have to find some pics. Folds flat, about 3/4" thick.
