Kia orana Jackie,
As far as I am aware the glottal stop is not a character of the Cook Island Maori alphabet. I also don't have a contemporary translation for such diacritical marks as the Glottal and Macron.
The use of the Diacritical marks is a recently established initiative aimed at helping non native speakers to learn the language. Prior to the advent of the Bible, Cook Islands maori was not a written language and no visual aids were used to help people recite their language. The only Polynesian people I know of that had a writen language were those of 'Rapanui' or 'Easter Island'.
There are other consonants within the Cook Islands language F, S, L, W are also used in some dialects and the vowels can take on short or long form, with glottal or without glottal.