I can recommend contacting them anyway. The worst that can happen is they confirm that they can no longer supply replacement parts.
If you are lucky they may be able to replace it for you.
I bought a pair of Heco Superiors a long while back. They were ex-demo from one of the Derby HiFi shops and one of the tweeters was fried. They discounted the speakers heavily and gave me contact details for the manufacturer. They sent a replacement tweeter free of charge and I'm still using the speakers every day thirty years later!