Speedy Jim wrote:

Get the finest tooth hacksaw blade. Break off
one end, so that you can work the teeth in closer.
Hold the blade vertical inside the brass fitting.
(Use a good glove)
Scrape the threads with the teeth as you revolve
the blade around the fitting opening. With some
effort and patience you should be able to extract
the broken brass threads.

Take the old tube to a big hardware store
(I doubt that BigBox will be much help.)
There are 3 different Refill tube (Overflow) diameters.
Match one up. Saw cut to proper length.
Use sealant (Loctite) on the threads.

Jim

Jim thanks again. This worked like a charm. The toilet is up and
running (pun intended).