As you've already got power to the cluster you need by soldering the wire to the bulb etc, that will keep you going for a while but in the meantime why not look for a secondhand cluster with the fog light in? If you're in France and it's a requirement, chances are that there will be scrapyards with the right sort of cluster you need.
Then you can "pretty up" the connections and have a proper bulbholder too!
