Jim...
My PD9260C converter/charger manual calls it a rj9 4p4c type modular connector...
The RJ9 is a standard 4 wire phone connector...
My PD9260C WIZARD Pendant has the cable permanent on the pendant end and uses a male RJ9 modular conenctor on the other end of the long cable...
You can find long lengths of RJ9 Male to Male cords but a RJ9 Male to Female is usually a short adapter type cord.
I would look on AMAZON to see what they have...
I like RoyB MA's comment on splicing in a four wire cable in the pendant unit.
Roy Ken
RoyB VA