The term 'serpentine' suggests a belt that flows sinuously around the ancilliaries that need to be driven - PAS pump, alternator, aircon pump, water pump etc.
More likely what you're after is a 'ribbed belt' set up, which is fitted to later motors such as the 2E motor etc. This drives some of the ancilliaries more reliably than the earlier 'V-belts'. It's the wide one in the pic here:
