DIGITAL AUDIO TAPE MACHINES start selling in Japan this month. Aiwa, Sony, Matsushita, and Sharp are marketing DAT players priced from $1,250 to $1,335. Blank DAT tapes sell from $8 to $13.35 apiece, depending on length. Controversy over the possibility of pirating compact disc recordings with DAT technology is delaying the marketing of the machines in the US. KNOW WHERE TO FIND any rare TV shows? Fuji Photo Film USA has teemed up with New York's Museum of Broadcasting to help locate missing copies of historic telecasts such as the Army-McCarthy hearings and the TV work of James Dean and Humphrey Bogart. On the museum's current ``most-wanted'' list are: Super Bowl I, the opening of 1939 World's Fair, and the pilot of ``All in the Family.'' THE STRATFORD FESTIVAL (Canada) production of `The Mikado' opens at Broadway's Virginia Theatre on April 2 after two preview performances. Directed and choreographed by Brian Macdonald, the 1982 revival of the Gilbert and Sullivan musical has toured Canada extensively, visited New York and other US cities, and appeared at London's Old Vic. IN SOUTH FLORIDA, a regional outdoor theater circuit is on the drawing boards. Construction has begun on the state's first outdoor amphitheater, the $12 million Palm Beach Pavilion; Fort Lauderdale has approved a developer's plan for a $23 million complex; and a third theater is being proposed for the Key Biscayne area. The Palm Beach Pavilion, with 7,000 roofed seats and 8,000 lawn seats, is due for completion in 1988.