Tempted to get this:
(It looks as if an SO3 would fit clamped/bolted to the workbench top)
But the price is way out of line with what you’re getting — probably could work up something similar for much less.
EDIT: Found the product page at Home Depot:
Unfortunately, only 13" depth from the surface of the folded workbench to the back, so probably won’t quite fit (though one would be tempted to cut out the back to allow it to fit).