A good place to start collecting information on Chinese opium pipes is
Arts of Asia magazine March-April 1995 article by Benjamin Rappaport, "The
Chinese Opium Pipe: The Art and Beauty of an Evil Custom." This magazine
should be in most university libraries. The pipes illustrated here are
'collector' opium pipes made of precious materials, but the bowl shapes
should help you with your find. The simpler, everyday opium pipe has been
the subject of a number of archaeological reports from Western U.S. sites,
some have so much detail that one would think that the author is obsessed
with them. You might contact Priscilla Wegars at Asian American
Comparative Collection at University of Idaho at [log in to unmask] to see
if she has a bibliography.