The best place to shop for Souvenirs
For the best, most diverse selection of Costa Rican souvenirs there is a well-known place called the MERCADO MUNICIPAL DE ARTESANÍA. Any taxi driver will know exactly where that is.
My buddy Marco Salazar is in booth #76. He has the most unique items that are affordable and make excellent gifts for your friends and family back home or for yourself. He sits there all day and makes by hand, chains from a big roll of metal. Then he attaches in a unique way, semi-precious stones. His stuff is beautiful. If he had a separate shop in a mall he could easily charge 10X what he charges in his little booth at the Mercado. I buy earrings and necklaces from him whenever I go down to San Jose. I buy them as gifts and then keep them myself (don't judge me!).
Anyway, that's my best suggestion. If you mention my name, he'll give you a little discount on his already reasonably priced treasures.