We have completed a button for the BWG / BCG and a cable with a LANC micro controller. This board will work with any camera that takes a LANC signal, I have tested it on a C300 see below.
This same cable it will also trigger, the BMC, C100 and C500. With a different cable the button will trigger the Alexa. We have a almost finished cable for the Epic and Scarlet but it will most likely require a rocker switch, I would like to find something that will fit into the opening for the button so you could just swap it out. Sorry no F55.
I have a four pin Hirose. This button is green I have a black and a stainless steel (+$10) buttons coming in soon, you can also get red, white, blue or yellow.