Broken gas burner ring?

One of my Hygena burner rings has fractured into several pieces the problem being I don't have the model number to order a spare part. The cooker is integrated and was in the house when I moved in (about 17 years old). The hob is embedded into the kitchn work top so I can't get to see the model number and the built in oven underneath it is Tricity Bendix (of which I do have the model number).

Does anyone have any ideas how I could get a new burner ring for this?

Dee
February 2011