The Community of Tribunj informed us that they issued a contest for design of the coat of arms and the flag. The Contest is issued in the official gazette on 13 February 2008 available here http://narodne-novine.nn.hr/clanci/oglasi/492416.html
The deal-line is 90 days from the issue date.
The official web site of Tribunj is at http://www.tribunj.hr
Updated 21.11.2014.:
The Community of Tribunj repealed the contest on 4 February 2009 (cf. Odluka o poništenju natječaja za idejno, likovno i grafičko rješenje grba i zastave Općine Tribunj, 04.02.2009. Službena web stranica Općine Tribunj, www.tribunj.hr), and eventually on 16 October 2014 adopted a new set of symbols (Statutarna odluka o opisu i uporabi grba i zastave Općine Tribunj, 16.10.2014, Službeni vjesnik Šibensko-kninske županije, br. 12/2014, 13.11.2014.) designed by the Heraldic Art, published on the Šibenik Portal (“Općina Tribunj dobila vlastita obilježja”, Šibenski portal, 29.10.2014.)