We don't have synonyms for yupon yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are upon, yukon and jupon.
(n) :
(now uncommon) Alternative form of yaupon. [The yaupon holly, Ilex vomitoria, an evergreen holly shrub with white flowers and red or yellow berries, found in the south-eastern United States.]
(n) :
(now uncommon) Alternative form of yaupon. [The yaupon holly, Ilex vomitoria, an evergreen holly shrub with white flowers and red or yellow berries, found in the south-eastern United States.]