My own 870 Police model started life as an 870 Express, then received a 20" smoothbore deer rifle with iron sights. I found a factory Remington magazine extension tube with the bayonet lug, which I thought would complete the whole picture. But now the magazine tube extension has no support from the barrel, relying solely on the mag tube's threads, and it doesn't really stay together well when lugged aropund with the sling. I need to tie the bayonet lug sleeve to the barrel somehow to prevent the mag tube rotating on it's threads, preferably by the heatshield's clamp bolts. So what I may end up doing is fabricating and parkerizing two metal strips to bolt the lower tube back to the heatshield bolts, unless there's a better alternative out there. See the picture below. I'd welcome any suggestions. And thank you for the references, although I have a feeling such things are probably long gone from Scattergun's inventory by now.
Darin