Bummer!
I see some on eBay at the moment; also I think Amazon. A quick look around suggests it's been discontinued. That's a pity, the phenolic diaphragm is said to sound much cleaner and more relaxed than the titanium one. I haven't listened to the titanium myself. I have some big-ass JBL 2441s with Ti and they do have the "tinfoil" character, so I know I don't like Ti that much. But I am familiar with the ST324 in the Climax, and to a somewhat lesser extent in the Straight 8, and I personally do like it - especially with the Climax tweaks.
For what it's worth, the Raal ribbon is better. However, all ribbons including the Raal have been really problematical as far as crossovers go. We have a decent setup at present in the Bottlehead Big System, but it's probably 60% experimentation vs. 40% measurement/calculation, and it's a multi-amp active crossover setup that has been tweaked for years. I don't know any other ribbon that can go low enough reliably - especially if you like Nine-Inch Nails.
I do have one pair of ST324 in the back corner of the lab (basement), new but in mismatched boxes for some reason, with the same label. I'll never use them, so if you or anyone else wants them, let me know.