Subcaliber ammunition

I need to find me some insert adaptors.

See, there have been several times in my law enforcement career where I've needed to put down an animal in the city. Sometimes it's a rabid skunk. Sometimes it's a dog that's bitten someone for the last time. Occasionally it's a dog that has a "death warrant" issued. On one memorable occasion, my lieutenant had to put down a rogue emu that had been running in and out of traffic. (I can't make this stuff up, folks.) Or it might be an animal that's been struck by a car and needs to be put down. While of course we make sure that we have good backstops, people get worked up over identifiable gunfire, sometimes. Firing my pistol is LOUD. Firing my shotgun is LOUD. I don't carry around a .22 LR rifle, which would be the best solution in all probability.

But they make these little inserts. I've seen them advertised, and even recall a magazine article on 'em back in the 1980s. They're special adaptors to fire centerfire handgun ammunition through a shotgun. Well, in my car is an 870P shotgun with iron sights. If the thing is halfway accurate (say-- hits a pie plate 5 times out of 5 at 50 yards), then I see no problem with getting a .38 Special adaptor, and putting a 158g LSWHP in it, and euthanizing said critter with minimal fuss, and far less noise than a full shotgun blast or pistol report would give. My theory is that the shotgun barrel will act to suppress the report of the subcaliber round in it. This theory, of course, is absolutely untested. :)

But I can't find the dadgumed company or companies that make or distribute 'em!! All I've found so far is
this thing, which fires .410 caliber shells in a 12 gauge shotgun.
Hm. The price is fairly low. Perhaps I'll pick one up and try it with slugs. But it's still not precisely what I had in mind.

Anybody have a link or a phone number?