Do any of you know the name or numerical designation of this type of barrel connector where the cable end has both the barrel and the inner tip (presumed to be positive)? This is from a new Xfinity Modem and the barrel itself is about 3/16th of an inch across, or a touch less than 5mm.

The plug has both the central pin and the conductive barrel whle the receiver end in the modem is weird looking with a skinny rubberish central protrusion that has a very small opening for the pin, and then an annular space that the barrel part inserts into. Typically, the receiver has a pin (male) and the plug has the barrel but in this case the pin and barrel are both on the same end (coax style).
My goal is to find an adaptor so I can connect one of my conventional DC cables and use my LPS to power the modem.
Thanks for any help.
BTW, I did find this (below) on Wikipedia, so it is apparently a male version of a coaxial connector plug, but it is of no help in finding an adaptor.
"This less common type of plug is similar to the female version, but the center pin is of male type."

Male version of the coaxial connector plug