We search for a non-SM-like CP-odd Higgs boson (a10) decaying to τ+τ- or μ+μ- in radiative decays of the Υ(1S). No significant signal is found, and upper limits on the product branching ratios are set. Our τ+τ- results are almost 2 orders of magnitude more stringent than previous upper limits. Our data provide no evidence for a Higgs state with a mass of 214 MeV decaying to μ+μ-, previously proposed as an explanation for 3 Σ+→pμ+μ- events observed by the HyperCP experiment. Our results constrain NMSSM models.