Steven Goldstein, president of TradeWeather.com, an on-line weather derivatives company, is among the thousands still unaccounted for following the Sept. 11 terrorist attack on the World Trade Center in New York. Goldstein, who launched Tradeweather.com in 1999, moved into the North Tower of the WTC about three weeks ago. The move followed Cantor Fitzgerald's acquisition of the company which was incorporated into the broker's emissions trading group, according to a market official. Cantor occupied floors 101-105 in the North Tower. Officials at Cantor did not return calls.