I think you pick it up in el topo's asylum, I've already missed it, could anyone tell me where exactly does it pop up? Thanks

I received the Pirates mission from El Topo in his office after I went to collect the payment for completing the Asylum Patrol mission.

While playing through a second time the mission was not offered so I reloaded a previous save. This time I went to El Topo's office before clicking any of the other conversation links and still no mission was offered. I then went to Thalasso Place and talked with everyone except Charlotte Gillmore. Then I went back to El Topo's office and He offered me the Pirates mission.