Although new technology promises to do away with toilets that use water, the two types of toilet most common throughout the world are the toilet you squat over (kloset jongkok) and the toilet you sit on (kloset duduk). For those accustomed to using the squat toilet, the other kind is called a 'western-style toilet' (kloset gaya Barat). The technical term for such a 'sitting toilet' is, however, 'flush toilet' (kloset siram). So there are several alternatives; the most common, judging by a Google search, is 'flush toilet' (3,960,000 results). However, to retain the sense of 'duduk', depending on the context (which the asker did not provide), 'western-style toilet' is an alternative, yielding 331,000 Google hits.

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Note added at 1 hr (2010-08-15 11:22:44 GMT)
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To the ordinary Westerner, particularly those who have not traveled to the undeveloped and/or developing nations, a toilet is something you sit on. The squat toilets are quite foreign to the great majority of Westerners, who eagerly search out a 'proper' toilet, i.e., a toilet you sit on, when they travel.