Check out Taxitemplarios. They will transport from Lisbon to Coimbra, I believe. We are using them from Tomar to Conimbriga.
I found their name on the Stingy Nomads website.
This site is run by Ivar at in Santiago de Compostela.
This site participates in the Amazon Affiliate program, designed to provide a means for Ivar to earn fees by linking to Amazon