No real answer to that question apart from finding something similar that will fit !
This thread is interesting. Celestion Ditton 44 - HF 2000 tweeter replacement? - UK Vintage Radio Repair and Restoration Discussion Forum
And of course replace as a PAIR ! ....or buy another set with a bass driver blown then you will have some spares !
We can use objective tools to help us accomplish subjective ends. Making music has always been a combination of the two that can complement each other. ..........JR