Yes, it is unfortunate that Adafruit discontinued that device because it was very easy to use.
As a replacement it should be possible to use a HC-05 Bluetooth module, which is very common and easily found. I have not tested this myself, which is why I have never had the occasion to put instructions for it in the Wiki.
One annoying feature of the HC-05 is that it cannot accept 5 volts signals on its receive pin (RX). Therefore a voltage divider must be used between the TCB Serial 1 Tx pin and the HC-05 Rx pin. If you have the new TCB sold by Torro, these have already been added to the board so you don't need to worry about it. But if you are using the old TCB sold by Hobby King, then you have to add them yourself between the TCB and HC-05 (I have attached a picture below that shows the voltage divider).
In either case you need to make four connections:
| TCB | | HC-05 |
| Serial 1 Tx | > (voltage divider) > | HC-05 Rx |
| Serial 1 Rx | < | HC-05 Tx |
| Gnd | = | Gnd |
| +5v | = | +5v |
You need to pair the HC-05 to your computer, and whatever COM port Windows assigns to it, select that COM port in OP Config. On the TCB you need to set Dipswitch #5 to the OFF position, this tells the TCB to communicate over Serial 1 instead of using the USB port.
Those are the general instructions, but I would not be surprised if there are other details that would have to be figured out if one actually tested it. Unfortunately I don't have any boards in my possession at this time so I am unable to test it myself.