Military gear that is not legal for sale shows up for sale on eBay, Craigslist and the like, on a pretty regular basis; but there are only a few places the gear could come from. Somebody I know purchased some re-breathing equipment, used by Special Forces (Navy Seals) that is not sold (legally) to the public for a couple hundred bucks on eBay (probably came from a fire department). Sad to say more than a few cops and fire fighters are crooks, and honest colleagues too often look the other way. Alas, police and fire fighters are portrayed as figures of authority and heroes, endowed with special special traits above dishonesty - they and the agencies they work for are uncritically revered by the press, politicians and other public agencies so illegal activities are ignored.
.
https://theintercept.com/2015/03/26/missing-military-tech-ended-ebay-craiglist/