I am specifically interested in firms that have experience selling online multi-cultural advertising. We have the product offering; we are looking for rep firms that can sell the products.
A search engine will be the best database in this circumstance. Your inquiry is specific enough that any firm meeting your criteria should be easily discovered through a combination of carefully selected keywords. Any firm not revealed either (1.) doesn't fit your criteria, or (2.) has no real understanding of online marketing. If they can't do it for themselves, what would make you think they can do it for you? Trust your search engine.