Ammo for the 9mm Ultra (Police) is not easy to find. The 9x18 ammo is readily available but WILL NOT work in it. Quite a difference in bullet diameter for starters.
The Ultra is basically a (1mm) longer version of a .380, which some people claim it will fire in the Ultra's chamber, but fits sloppy.
Ultra ammo is out there, just not on most shelves. If you find ant, order all you can cuz it may not be found again.