Since that is such an old speaker, doubtful you will be able to find an exact replacement. You'll want to change the tweeters on both speakers you have. Unfortunately, whatever you get will probably not be an exact match. It may sound worse. It may sound better.
I'd check Parts Express and Madisound for tweeters.
A forum community dedicated to home theater owners and enthusiasts. Come join the discussion about home audio/video, TVs, projectors, screens, receivers, speakers, projects, DIY’s, product reviews, accessories, classifieds, and more!