Dear Liz the Squeak,

The original is (I think) in the Bodleian.

The transcription often used by scholars is:

NORRIS, Edwin, The Ancient Cornish Drama (2 vols. Oxford: Oxford University Press, 1859; repr. London & New York: Blom, 1968).

The Tale of Seth and Adam is (naturally) in the Origo Mundi (i.e. the first of the three plays).

The variant from Jewish oral tradition has also been printed but I don't have the ref to hand.

Gans gorhemmynado an gwella,

Crowdercref