Yes, when you mentioned installing a different tweeter, that was my first thought - the unique mounting arrangement. I have a surplus of speakers already, so I don't need them for myself. Anything I do with it now, will be an effort to avoid ditching them and maybe I would give them to a friend or relative. Even if I had both speakers in fully functional condition, I doubt they'd be worth much. Probably not much more than the cost of a new tweeter. Although I hate the thought of junking them, I don't think I would go with a different tweeter - I'd have to buy 2! I'm not about to invest that much into this. So, if I can't come up with an OEM tweeter, I'm afraid they'll consigned to the dust heap.
Thanks a lot for your interest, Doc!