Was having a rummage around the farm sheds yesterday morning, looking for something to use as a carcass tray in the the back of my pickup, without spending any money. Eventually came across an old stainless steel table that had come out of a catering premises, and was currently just kicking around surplus to requirements. The table top was only held on with some sticky stuff that had long since crumbled away, so I was able to simply lift the top off the base, turn it over, and hey presto! A lovely stainless steel tray, measuring 4ft x 2ft6ins.
A few hours later and I put it to the test with a nice fallow prickett. Perfect.