Peter, it is the Receiver-Drier which acts as filter and absorbs unwanted moisture if present in your A/C system. It can be mounted anywhere on the high-pressure side. I have moved mine in front of the Right rear Wheel behind the Splashield. It is a service part and need to be changed frequently, at least every time your system has been exposed to atmospheric pressure/air. You can use any Universal filter provided the connections are the same. i.e. O-ring or Flare.
I am not sure if you can find a replacement Filter that screws into the Block on the Photo you attached. But never say never
One thing the Panteras Aircon lacks is a pressure Switch that serves as a protection for the Compressor. Many filter has an option to screw one on the Filter directly. electrically it is connected in series with the Compressor clutch and If system has low pressure it isolates the Compressor and prevent it from damage. Same for overpressure, usually the range is 2-30bar so anything above or below will shut it down.