please help an audiophile's widow

Is that a whole speaker, or a driver?  If it's a driver you can often find them on ebay.  Google is your friend. 

I think this is what you are looking for:

Paradigm Tweeter

@dill not sure if the -030 at the end makes a diff.

See if the Paradigm speaker model (not the tweeter, but the whole speaker model) is listed @ the bottom of the following (linked) page.

If it is then the tweeter listed should be a suitable replacement mounted to the existing tweeters faceplate.

https://www.parts-express.com/Peerless-D27TG-35-06-1-Silk-Dome-Tweeter-264-1022?quantity=1

DeKay 

@erik_squires Looks like the 3 trailing numbers are for the same tweeter/driver, but different waveguides for different model speakers.