Darn you for making me think!Find a used marlin Camp 45 and spend the rest on ammo.
If I started with a Camp Carbine in 45, I could SBR it, maybe add a custom stock, and have something that looks (from a distance) like a Reising. That would be almost as cool as a UMP clone.
There are too many good (and potentially expensive) ideas floating around this board. I shouldn't spend so much time here.