The broken piece is the fuel inlet. Most bing's use a banjo bolt style. That's a bing 12mm carb, you could buy one off ebay for cheap but be warned that they are crap and the idle adjustment screw is drilled incorrectly so it doesnt hit the slide so its useless. You could use all the parts off the copy to fix your though.
Some carbs have two cables for a push-pull style throttle.