I use the XPT wall transmitter paired with the 4-button control panel (XPT4). The version I have is actually Insteon from memory so it has an LED to indicate if the light is on/off. It works quite well. That said, from reviewing the manual, the TK184W appears much more flexible with its configuration. The XPT can be changed from 4 button control to 3 button with dimmer by changing the face plate. The ACT unit appears to be able to switch by programming. If there is an LED behind each button, that would be a really sweet unit!
That said, I have no idea where to get one other than recommending watching ebay.