They look like Rapidfire shifters, which have been obsolete for 20 years now, unless you found a NOS pair it's very unlikly you will find spares or a replacement. The rapidfire shifters used the thumb to shift up and down, not the thumb and finger like the Rapidfire+ shifters which are normal now.

Yes they have broken, but they were 20 years old, no big deal, time for an upgrade, being realistic, a new mid range bike will be better in every respect to a high end bike of 20 years ago.