HI,
sorry but i think there is a term for your burner,politely it,s passed it,s useful life,what make is it?? .There is no way you can glue it together,and the other burner looks about to go the same way, should it have a hole in it?.It is all part of the burner,the pipe underneath is the jet. The gas is difused by the broken part which produces your ring of small flames .As a registered gas engineer please buy another one
regards Trev