We don't have synonyms for tappers yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are trappers, tapper and sappers.
(n) :
(sports) An assistant in the sport of paraswimming who taps blind or visually impaired swimmers with a pole to indicate when they should turn around.
(n) :
(sports) An assistant in the sport of paraswimming who taps blind or visually impaired swimmers with a pole to indicate when they should turn around.