We don't have synonyms for petasos yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are petasus and pegasos.
(n) :
Alternative form of petasus. [(historical) A broad-brimmed, low-crowned hat worn by the Ancient Greeks and Romans, especially for travelling, and as often pictured to be worn by Hermes (or Mercury); (later also) the brimless winged cap worn by Hermes in later artistic depictions.]
(n) :
Alternative form of petasus. [(historical) A broad-brimmed, low-crowned hat worn by the Ancient Greeks and Romans, especially for travelling, and as often pictured to be worn by Hermes (or Mercury); (later also) the brimless winged cap worn by Hermes in later artistic depictions.]