Just an (extremely belated) update on this, in case anyone is interested. I ordered a throttle new from Ebay, there's loads of different ones listed but to be honest they all look very similar.
It only cost me about £3 and took a few weeks to arrive from China.
Fitting it was very easy, it just clipped into what was intuitively the right socket.
I was pleased to see that the bike already has a wire leading from the front brake leading to the controller, which is responsible for cutting out the motor when the brake is applied when the throttle is open.
The only thing that could be considered a problem is that the Coyote Connect doesn't have space for the throttle on the handlebars as it comes - you will have to get your Allan keys out and move things around (it wasn't a problem for me, because I am now running the bike as a single speed, so I have put the throttle where the old Revoshift gear selector was).
I hope this will be helpful to anyone
