/N/ : suggestions please

I need a (di)graph for the nasalysed velar (/N/) of my TUNU language. This
phoneme occurs only in the end of a word after a vowel. I write it "q"
currently. Other graphs already used are : a, c, e, h, i, k, m, n, o, p, r, s,
t, w, y. I'd like to keep the phonology very simple (as is the grammar to my
own standards) and as easy as possible to read for readers not versed in
phonology because I'd like to make the grammar page legible without too much
pain and ennui (like Carlos, Sally, Herman, Christophe and others succeeded).
Thanks for your contribution.
Mathias