Those tweeters are a custom version of the RAAL 70-20. It is an OEM part that, to my knowledge, is not available through companies like Madisound (which carries most other RAAL tweeters). Our version is built with amorphous core magnets and only has one set up inputs rather than three on the standard 70-20. So even if you could purchase a 70-20, it would not be quite the same as our version.
The ribbon elements can be replaced if everything else is still working. If not, you will need a new tweeter and we can set one up for you.