I think perhaps your best bet would be to research existing papers on venom composition. Some of the antivenins, although not marketed for certain species, can be effective on them. For example, there is a close evolutionary link between
Echis (sawscale/carpet vipers) and
Atheris (bush vipers). Therefore, although there is no antivenin specific for
Atheris, Echis antivenin has effectively neutralized some
Atheris bites.
I'm not sure about the availability of antivenins overseas; I know that there are banks here in the US that stock them and you pretty much have to have it flown to a hospital local to you in the event of a bite.
I like the website
WCH Clinical Toxinology Resources for researching snake species and appropriate antivenins.
Let me know what I can do to help!