gunner,
I can't help with factory ammo,but if you or your buddy can handload,you shouldn't have a problem. I use 444 Marlin cases to load for my 410 pistol(I have papers)and the dimensions you gave seem to show they would work for you with a couple modifications. You would have to shorten the cases by 1/4" or so and maybe thin the rim.I would suggest thinning from the rear and use pistol primers.If still not thin enough, take a little off the front side.
Mike