Replacement Crucible for Centrifugal machines are easily available.
For US machines I know of only 4 sizes/types If it is small as you
described then there are only 2 that you have to choose from. They
are pretty reasonable and I would buy the one closest to your size.
Minor adjustment to you Cradle and Crucible holder can be made to fit
If you can check Swest or older catalogs you might find an
illustration/sketch with sizes / dimensions. This may help you
identify the one you need.
You are welcome to send me a sketch of your crucible with dimensions
so I can match up with what is available out there.