Demon carb electric choke

The kit you need is Barry Grant/Demon # 421440 and is discontinued. I've looked all over and cannot find anything. You may end up having to hawk Ebay for a whole carburetor that maybe has a broken base plate or something, or just slap luck up on that kit. But there's you a part number anyway.
I just went through this. MY carburetor guy looked and looked and found ONE choke kit remaining in the entire country....In Utah of all places. If he hadn't found it there, I would have had to make my own butterfly. The choke housing and fast idle cam setup look like regular Holley stuff but the linkage rod to the shaft and the butterfly appear to be Demon specific.
Check out THIS thread:
Trying to improve cold starts with a Demon 850