If you have the pro, I'm working on this. I got a stand and made some 3D printed adapters for the cymbal. I'm using a Roland CY-5. Currently I just use a momentary switch on the pedal of the stand. Work for open and close. The module accepts an input of 0K ohms to 50K ohms for the hihat control. So a simple slide pot should do the trick. I plan on mounting this in a box near the pedal and connect it with a rod. The pot are dirt cheap. $2.50 each at places like Jameco. But they charge shipping and you have a $15 min order or a $5 surcharge. Well, order some panel mounts and a few extras, maybe a project box to mount it and you are at $15. I plan on 3D printing my housing for the parts so that it fits nice on the stand base.
No other magic parts are needed. The cable from the module is TS only and it just looks for resistance. A rapid change splashes or chicks. It should work for a while. Maybe i can try a rotary POT.
I think the best solution might be an encoder strip with a laser sensor attached to an Adrino. The Adrino encodes the signal and sends the variable resistance. No parts to wear out. Another time maybe.