I just finished the final stage of my darkroom remodel job and need some help locating a replacement water filter cartridge for my PAKO no. 58-146 hot water filter. It calls for a no. 58-513 replacement cartridge and I'm having a devil of a time finding one. This filter goes with my antique Leedal thermal valve system that seems to be long discontinued. Any links would be greatly appreciated, Thanks, JohnW