Unfortunately, they don't make a regular bit for Combi-Flamers, but I've used a conversion I've seen online to make mine.
What I do is clip the Flamer barrel off the original Flamer bit, and then file down the very tip of a Boltgun. File the rough end of the Flamer barrel, and then glue the barrel to the end of the Boltgun. Literally takes minutes, and it makes a pretty convincing Combi-Flamer.
Good luck!