Funny, but I used to use a milk crate to film shows at the Wetlands in NYC in the late 90s. I put the crate on the seat across from the stage and then taped a phone book to the crate for more camera height. And then somehow I stood on the edge of the crate where the lip was stronger than the middle of the crate without falling off. By the end of the night, my feet were killing me. But it had to be done this way because the Wetlands stage was really low. I needed the extra height without buying a new tripod.
BTW, I did this 3 or 4 times to film Zero and Kimock bands. I literally walked into the club carrying the crate. I wish you luck in your search.