NEED 4-pin Bias Switching Plug for Johnson Thunderbolt

[Jan N0JR]

I am loking for one or more of the 4-pin plugs that connect to the 4-pin
steatite bias-switching (transmit/receive) socket on the rear of the
Johnson Thunderbolt linear.  I do not know the particular model of plug
required--don't recognize the socket pattern.  Any leads to plugs or
model designation would be appreciated!!  Many tks es vy 73, Jan N0JR
--
"There is no end to what you can accomplish
if you don't care who gets the credit."