Hi 001.
Yes - your correct there is no Diaphragm kit available which is a crying shame.
I'm a bit nervous about ordering a Complete Full Spare and finding out that it's not exactly the same as the Existing Working Tweeter.
If Spare Diaphragms were available i would purchase Two - just in case, they were not equal i could replace the Two.
As silly as it sounds - I know, but i have learnt from previous experiences.
With regard to Willand's Reply - I tried Simply Speakers a week back and they said it's a common issue and that they don't have access to replacement diaphragm kits either - Which Frustrates them as well.
In contemplating just retrofitting something else into the Enclosure, as it does seem the originals are not that Reliable anyways.
I have a spare Set of Vifa Tweeters i might look into Mounting.
I'll keep you posted
Cheers
Ren - New Zealand