Amazon.com: ienza 2.5mm Male 3-Pole to 3.5mm Female 4-Pole TRRS Headset Jack Adapter Compatible with Panasonic Cordless Phones to Headsets or Headphones with a 3.5mm TRRS Plug (Mic & Headphone) : Electronics
Delock Products 65459 Delock Headset Adapter 1 x 3.5 mm 4 pin Stereo jack female > 2 x 3.5 mm 3 pin Stereo jack male (CTIA pin assignment)