True, VT if using just the cotterpins on both sides of the hitchpin as I described. However, I've seen some miniture padlocks at both HomeDepot & Lowes with skinny shank loops that might be able to wiggle thru the cotterpin hole of the chrome hitchpin. If you get two(2) minature padlocks sold as a pair that are "keyed alike", then you'd have a padlock on each side of the hitchpin using the same one key. I'm sure the right minature padlock is out there somewhere that would fit in those tight confines at the hitchpoint.
In that case that's the exact solution Sue and I discussed via PM. I might give this option a try, I've got two extra angled pins in the garage that would serve well for testing. Now to find the time.