I hand wired a TR board that also brought out the paddle inputs. I had a number of RF relays in my junk box so that is not a problem; the RF relays are my TR switch and can be driven (very carefully) from the radioberry signal on the 20 pin connector.
A winter project is to re-do it on a PCB and I can make that available when done, but I will build it using the Teledyne relays I have on hand which are, unfortunately, expensive to buy. I got them from an estate.
Happy to consult and share as I do this. Probably the key issue if you build your own is that the PTT signal off the radioberry is 3.3V, and 10 mA, but you should double check that. My relays are 12 V so I used an FET to an opto-isolator chip to both keep the current on the pin both low and safe from damage. Once damaged, I believe you need a new radioberry.