If it was mine, I would drill small holes and insert some Arrow staples to hold the pieces together (something like surgical stitches or staples). I would then cover the whole thing with a layer of J-B Weld (actually, I would put a little J-B Weld in the crack prior to installing the staples). If I was real ambitious, I might even paint it black (although a magic marker would also work).
I like the staples as they are flat and fairly sturdy.
Something like this (except the staples would be shorter with the gap removed):
