I actually made one out of an old 4 foot foldable table. I unscrewed the legs, cut a bench rest top out of plywood with my jigsaw traced that pattern and cut another, glued and screwed the two together, bolted the folding legs from the table on my new bench rest top....the trick here is inserting wooden dowels in to the legs of one side to match the 2 x 4 riser on the bottom to offset the legs so it will fold up more compact. I can send you some pictures of you want. Mine is about three foot long, true ambidextrous, solid as a rock, not very heavy and the best part is that it was cheap. I have 0 in a donor table from an old school, 30ish in the plywood, a couple dollars in screws, ,and a little time invested.
I wish i could say this idea were mine but i think i stole it from an old article from varmint hunter magazine......absolutely brilliant