There is a number of anti-emetic drugs that can be used for this purpose. Most are only available on prescription. Be aware that it may be necessary to fabricate a reason when asking a doctor to prescribe them for you.
An additional point is that all anti-emetic drugs have side effects. Some can be serious. If you have never taken these anti-emetics, it would be wise to take a test-dose in advance of your chosen day. This way, any allergies and hypersensitivities to a particular anti-emetic can be taken into consideration in your overall planning.
Some of the anti-emetics commonly used in conjunction with end of life drugs are shown in the following table which also states common drug names, available pill size, doses, recommended regime and possible side effects.
In November 2021, the medical journal, InSight+, published a warning for doctors that a person who suddenly asks for antinausea drugs without a medical reason should be treated as a ‘flag’. This may suggest that the process of obtaining these drugs from your doctor may be harder than was previously the case.