I had the same problem Ian.  I did a “temporary” fix with a piece of 1/2” Starboard shaped to span the holes where the break is.  To complicate matters further, one of the bolts was seized to the mild steel backing plate and I broke the head off trying to get it out.  The backing plate is quite a bit below the surface, and drilling it out left a hole that was impossible to rethread.  I used a Mr Toggle bolt which leaves a reusable female thread below the old backing plate.  It has held up beautifully for ~4 years...we’ll, maybe not aesthetically, but pretty is as pretty does.