Not too hard to do... I got a CNS carb with a cable operated choke and all it is is an older style shifter lever but the cable runs into the carb...
To convert a stock carb like the NT or Speed carb you would need to drill a hole in the choke lever to accept the cable then use a shift lever that could be mounted on the handlebar, stem, or wherever it would be convenient. You'll also need to fabricate a bracket to hold the cable, and maybe loosen up the nut that holds the lever so it can move freely so the cable could push the choke on and pull the choke off. If the cable bends too easily to use a single cable to push on/pull off, or pull on/push off, you could hold the cable straight maybe by hanging a weight to the carb end and tinning the cable with silver solder to make the last few inches of the cable rigid.
Another way to do it which would take a bit more fabrication would be to use a series of bell cranks and a long push/pull rod to a remote lever... This would look really cool if you can do it.
Then there's also the rigid cables used on older lawnmowers that can push or pull to control the throttle or choke... Check out a lawn equipment repair shop in your area and I'm sure they can help you on this method, which may be the easiest of the ones I've mentioned. The only drawback here is that these cables don't like tight bends so the cable will need to be routed in a way to avoid as many bends or turns as possible.