I forget who made it, but there was a PL/DPL decoder built into the same case as the BC760 scanner, and designed to be mounted on top of the scanner. Worked great.
More…. Made by Automated Industrial Electronics, there were several models of this gadget. The TF-1 is a basic PL tone decoder; the TF-2 added DPL capability and a new case matching the BC760. I forget what the TF-3 added; the TF-4 was the same as the TF-2 but was designed to be connected to a Pro-2004. It included internal memory which correlated to channels in the scanner, adding a PL tone capability to the radio.
The TF-1 was simple to hook up, but the TF-4 required several wires. I still have both boxes and the TF-1 is running on my Turbo Whopper Pro-2004, but without a manual there’s no way I can hook up the TF-4.