Hi! We have a lot of resources about magnesium as migraine treatment. I'm not sure how much of this applies to aura specifically, but if your doctor is on board with it, it's worth a try.
https://migraine.com/blog/migraine-treatment-series-oral-topical-magnesium
https://migraine.com/migraine-treatment/natural-remedies/magnesium-for-migraine-headaches
https://migraine.com/living-migraine/magnesium-for-prevention
Are you in a place where you have access to specialists? GPs are great at what they do, but they are exactly that -- general physicians. If possible, we encourage people to work with a neurologist or certified headache specialist whenever possible, because they usually have more specific training and expertise for migraine treatment.
I wish you all the best. Keep asking your doctor to pursue other options. Trial and error is so important. We're here for you! -Melissa, team member