It's not too late to build your own pine box! Gonna let neighborhood kids climb in, slam the lid, and shovel dirt on 'em. Wholesome family Halloween experience!
All you need is 6 6-foot 1x8s (top and bottom), 3 6-foot 1X12s (sides) and 4 8-foot 1x2s (support), plus a box of 1 1/4 inch wood screws. I spent less than $50 for everything.