Calling all archive-holders and reference-sleuths!

According to this citation
SftP activists associated w/ Science for Vietnam published "The Big Gun is
the Rain": a "report on the use and potential for geophysical warfare by
the US" in Vietnam. As SftP approaches its publication of a collection of
essays on geoengineering, such a report might make for a great candidate
for digitization and re-publication.

Do you know where we might find a copy?

Thanks for your help!