There are currently 9 Trebish/Trebysh names in the online telephone directory for the city of Chernivtsi. http://www.nomer.org/chernivtsi/fio_%D0%A2%D0%A0%D0%95_pagen...
. See the entries for ТРЕБІШ and ТРЕБИШ.
Unfortunately, I don't think that there are online telephone directories for the rural areas. Another alternative is to write to the mayor or administrative head of Tsuren to inquire if there are currently any families with that surname.