I have the same anchor light as the OP, and it does not work well. (it often looses contact as the pole rocks back and forth). The plug and socket are both like a half moon or "D" shape, and the contacts are on the flat side of the "D". I have never seen a replacement in any of the stores or online so far.
I gave up and bought a replacement that included a new socket. Now, just need to find time to install it!
_________________

"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings