While Olanzapine is mainly an antipsychotic medication, due to the fact that it works on Dopamine receptors(D1&D2), it sometimes also works as an antiemetic, but the latter is not it's main function. And Olanzapine has some unpleasant side effects, among them the most tedious is parkinsonian syndrome, that's why Olanzapine is a second line of antipsychotic drugs- which means the doctors tend to try something else first, only if the prime candidates are not working , only then they'll prescribe Olanzapine.
But if it's the only thing you could get, then you have to test whether it has the potential of causing you parkinsonian syndrome, you start with 10 mg per day, if after two weeks nothing happened, then you can proceed on trying 20mg or more.
So IMO, you should try to get a prescription for Meto, and treat Olanzapine as a back up resort. Wish you well and good luck.