Niggahiita in IPA?

Hello all,

For a chart I'm preparing showing SE Asian regional
variations in the pronunciation of Pali I want to represent
the normative pronunciation of Pali sounds (as described in
the grammars) in the International Phonetic Alphabet.

For the vagga nasals I have the following:

`n [angma / n with leftward hook at right]
~n [n with leftward hook at left]
.n [n with rightward hook at right]
n [n with subscript bridge]
m [m]

but would welcome suggestions as to how (if at all) the
niggahiita would be represented in IPA. N.B., I am not
concerned here with how the niggahiita is generally realised
in Buddhist countries today, only with the sound as described
thus:

Buddhaghosa:
"niggahitan" ti ya.m kara.naani niggahetvaa avissajjetvaa
aviva.tena mukhena saanunaasika.m katvaa vattabba.m.
       (Vin-a. vii. 1399)

Buddhapiya:
_a.m-iti niggahiita.m_
_a_kaaro uccaara.nattho, 'iti'-saddo
panaanantaravuttanidassanattho, a.miti ya.m _a_kaarato
para.m vutta.m bindu, ta.m niggahiita.m naama hoti.
rassassara.m nissaaya gayhati, kara.na.m niggahetvaa
gayhatiiti vaa "niggahiita.m".
       kara.na.m niggahetvaana, mukhenaaviva.tena ya.m,
       vuccate niggahiitanti, vutta.m bindu saraanuga.m.
       (Padaruupasiddhi 10)

I am also having some trouble with the vowels; the
descriptions in the grammars don't seem to be sufficiently
detailed for one to make a definite identification of all of
them. But I'll post my questions on these later....

Best wishes,
Dhammanando