Off the top of my head, Remington's Spartan line is imported, although those are clearly sporting shotguns.
Hence why we shouldn't worry about a tactical shotgun ban. The 870 series is one of the most common "tactical" shotguns out there, let alone any sort of mod to an 1100 for some semi-auto goodness. Just no detachable magazines which I think is the real target here.
I know there used to be a mod for detachable mags for I think the Ithica or Mossbergs. But those were pump models.