with Taiwanese Mandarin I mean 臺灣國語, also called 華語.
All I find online, given how relevant China is today is the simplified script and PRC vocabulary, not the vocabulary used in Taiwan.
Even translators advertised as offering Taiwanese Mandarin translate into Chinese Mandarin.
Pleco is the dictionary app I use. It does a good job translating phrases I type in and supports a variety of input methods. It has traditional Chinese characters as an option and offers the zhuyin(bopomofo) display as an option too.