I bought a controller for my Janome 1600P which velcros on the the handles. It definitely controls the machine just fine. I am having trouble big-time with thread breaking, but I don't think that has anything to do with the controller.
I think it came from Grace Frame, but when I can I will be glad to look it up if you are interested. I did also get a new carriage that has handles on front and back. Grace Co. didn't think this would work, but it seems to. All together I probably spent $150