it's called a "chassis" chass-ee.
you will not find anything new. this chassis is almost 20 years old
your best bet is e-bay or forums like these... search the for sale areas. problem is that the tubes they used in the u5000 where junk. likely the one you have is dim, or worse has blown color guns in it.
your best bet would be to try and find a whole monitor or replace it with a television (depending on what your plan is)