ALTERNATOR PULLEY RENAULT MEGAN II 1.5 DCI.

This type of vehicle came with two types of pulleys: one with a vulcanized rubber seal and the other a ratchet-type clutch pulley. From what you're saying, your pulley is a ratchet type. Here in Argentina, you'll only find them at Mar Zen. The original is an INA brand, but it's not available unless you order it from Brazil.