With FX-305 (DigiKey# 1110-2188-ND) having been obsolete as of February 13, 2024 folks are sure to be looking for replacements. Fortunately, Panasonic has put out a notice for it, the recommended replacement is FX-502 (DigiKey# 1110-1658-ND)
For reference here is the product change notification/EOL statement Panasonic released that lays out the discontinued parts and recommended replacements for this series: FX-300 Series EOL/Obs 17/Jan/2024