All I can come up with is the complete antenna.
I"m looking right at one and it's all one piece.
Are you referring to the antenna on the base unit.
The rubber coated ferrite antenna on the handset
is: PSSA1019Y for $10.62 from Panasonic parts.
https://www.pasc.panasonic.com/epartr/PartsList.asp The telescopic antenna on the base unit is:
PSSA1005Y and lists at $11.19
That's all I can do for ya.