Hi Robin, thanks for reaching out to Tundra Restaurant Supply with your question.
Unfortunately, we don't carry a brass burner for your OR-18W-C Wok Range, and in speaking with the manufacturer I learned that they actually don't make a brass burner ring - I was told all of their burners are cast iron. Additionally, our technician mentioned he can't remember coming across brass burners. They've always been cast iron in his experience.
That said, I feel bad not being able to get you the right part you need and still want to help if I can. In regards to leaky burner rings/burner tips we recommend making sure all tips are screwed in tight and not skipping threads. More often than not a loose burner tip will cause the burner to leak. If this doesn't not fix your problem I'm afraid you may have to replace the burner. Please give a member of our team a call at 1-888-388-6372 and we'll be happy to speak with your further.