"The New Webster's Library of
Practical Information, Grammar Guide," (Copyright 1987) pg 38:
9. The plurals of
compound nouns are generally formed by adding
s to the
principle word in the compound.
(some examples of that)
Sometimes
both parts of the compound are made
plural.
manservant : menservants
woman doctor : women doctors
...
Oddly enough it has exactly what you asked for...