The cost of original M1 carbines have dropped like a rock in the last 24 months, as the WWII generation of vets is 98% gone and the Korean War Vets are passing rapidly. They now go in the $750 to $850 range, even those without import marks.
The M1 carbine would be an excellent choice, especially if you carried soft-points, which put a big exclamation point on hits out to 200 yards.
Problem is, that finding more ammuntion would be hard, since not many stores carry M1 carbine ammunition any more.
I think the right answer is: .357 mag carbine by Marlin, .44 Mag carbine by Marlin, or Remington 870 20 gauge pump with 18 inch barrel and a full choke. All very light and handy, and very innocuous looking. Or, if you like, a .30-30 Marlin with an 18 inch barrel.
I still await those fearsome hordes of bikers who have determined to take over the world by conquest! (I'll see them in the deep woods!)
Manny