The diaphragms are for the 2 tweeters, which mine while bunged do still sound good with no resonance from the crack.....that said I should likely grab 4 and prep for a rainy day. They are 4 ohm and the selling indicated I could run them in series to present an 8 ohm load at the crossover. They are presently run parallel, although I could not tell, it seemed like all wires went back into the cabinet and not chained to each other, will have to look again, but I am assuming the seller knows his way around this speaker pretty well.
The super tweeter is a different matter. And falcon was basically like good luck with that as my best option....I think as mech says the HF2000 is my most promising source of a replacement, heck there is even one local to me now that looks like it would pop right in, but I have to get out the old one, and that is not an easy task with my bear paw hands, to figure out it's impedance..... There is also a SEAS 19TFF1 H0737
replacement recommended in place of the HF2000 by falcon.....but then if this one why not another? But overall I think your right audiomagnate orgininal or as close to is the best route.