Fairfax (Va.) County Educational Employees Supplementary Retirement System is conducting an invitation-only search for a global asset allocation manager to run up $300 million, said Alan Belstock, the boards executive director. New England Pension Consultants is assisting. Funding will come from existing equity and fixed-income managers; no terminations are planned. The board voted on Tuesday to make the move to improve risk-adjusted returns, broaden portfolio diversification and to improve portfolio returns in potential periods of subdued market returns, Mr. Belstock said. A selection is expected by September.