Metrical books (Orthodox) from Chagor, roughly dated between 1801-1933 (some years missing) are listed in catalogues of Chernivtsi archives. Later ones - most probably can be found in Hlyboka civil registry office.
Am providing researches in Chernivtsi archives and area too, if interested - feel free to contact:
lvivtravel@yahoo.comP.S. a bit out-of-dated databases show 3 persons with family name Kasiyan (Ukr. Касіян) in Chagor.
For now didn't find any (similar to) Trensay (nor in Ukraine) - should be a bit different spelling.