Caveat: mysterious wire connector thingy

Arthur really wants to buy some of these – somewhere online.
The problem is that neither he nor I have any idea what they are called. Some kind of locking electrical connector. But all of Arthur’s and my googling skills have turned up nary an image of one. So I’m putting this out there.
What is this called? I will attach three pictures, to show how it fits together. Overall connected size is about 1 1/2 inch long, but Arthur says there are different sizes.



[UPDATE: My brother Andrew got me the googlable name for these things. “Te Conn Knife Disconnectors“. Thank you Andrew and thanks all others who took the time to investigate! Logically (vis-a-vis Arthur’s affection for them), they are used in aircraft wiring.]