If you trawl the nether regions of the unicode font table (Insert > Symbol)
you'll find quite a range of diacritic characters and glyphs.If you can't
find full characters to your liking you can --
1. Do a Google for something like font +phonetic, to find a downloadable
font, or
2. Construct your own using a diacritic mark plus advance field plus the
character itself, eg ¯{Advance \l 5}a You can define these constructed
characters as Autotext entries if you need to use them repeatedly, or
3. Email someone who's published something using the characters you want and
ask them what they used.