The pan adapter is an option for the station monitor, make sure it is installed otherwise it is unlikely you will find one, even on eBay. One other important point, the Pan Adapter module is wired for 3.95 or 8.83 MHz IF, selected at time of construction. The IF can be changed but there is an IF transformer that must be changed, probably not easy to find, and the crystal is either 3.95 or 8.83 MHz. If it was used with HW-5400 it will be 8.83 MHz.