The Collaborative International Dictionary of English v.0.48:

Paradoxer \Par"a*dox`er\ (p[a^]r"[.a]*d[o^]ks`[~e]r), n.,
Paradoxist \Par"a*dox`ist\ (p[a^]r"[.a]*d[o^]ks`[i^]st), n.
   One who proposes a paradox.
   [1913 Webster]