Im not sure if the following will be your complete answer but it will probably give you some hint on the matter.
Its the book: "The Asatir, the Samaritan book of the "Secrets of Moses":Gaster, Moses, 1856-1939. p 178 and further.
Here is the link: https://archive.org/details/MN40245ucmf_0
Though both describe the last days/moments of Moshe's life, Mota Musa certainly isn't the same as Petirat Moshe. Hebrew and English translations are available here. In short, in Mota Musa, Moshe has a conversation with Hashem, at the end of which he is informed of the time of his death. He sets to prepare himself, but as many days pass, he eventually forgets. Then one day the Angel of Death arrives. Moshe asks to be allowed to say goodbye to his family. He is given permission to do so. Having said his goodbyes, Moshe enters his grave where he is greeted by the Angel of Death as he dies. He is then buried.
In Petirat Moshe, Moshe is reluctant to die. He ascends to heaven, speaks with Aharon and the Mashiach, then goes back down, has a big argument with the Angel of Death, even punishes him at some point - but all the while, heavenly voices come and inform him that he has less and less time left - until he finally accepts his death when Hashem promises that He Himself will take care of his burial instead of the Angel of Death.