What’s my next step, with 1 severe migraine yearly that sumatriptan, rizatriptan, and 3 clinical professors of neurology can't stop?

Age: 60. Female.
Weight: 60 kg = 132 lbs.
Current medications: Nothing save acetaminophen for mild headaches.

1. I’m in Hong Kong where:

[t]he majority of private doctors in Hong Kong are just Panadol-pushing sick note writers. Diagnostic skills are really sub-par here, specifically with GPs, but even specialists are generally mediocre and have no real interest in finding out what's wrong with someone.

you should remember that doctors in Hong Kong are a for profit business. I am from the UK so I'm used to public healthcare. It's quite a shock to come here where most people have health insurance and the doctor will treat every visit as an opportunity to sell you as much medication as your insurance will allow.

2. 4 years ago, I suffered severe migraine that 8 tablets of acetaminophen and Ibuprofen failed to stop. Thus I called 999 and was ambulanced to the public hospital where Tramadol Stada and Zofran were intramuscularly injected and succeeded in stopping the migraine. Thinking this a one-time episode, I didn’t act further.

3. 3 years ago, severe migraine recurred. Repeat 2 overhead. The next day, I paid $1000 HKD to see a neurologist who’s an Honorary Clinical Assistant Professor at HKU’s Faculty of Medicine. She prescribed me Cafergot. I paid $10K HKD for a Brain MRI + MR Angiogram with which she found nothing wrong.

4. 2 years ago, severe migraine recurred. I immediately took Cafergot, but it didn’t work. Repeat step 2. I paid $1500 HKD to see a neurologist, an HKU Honorary Clinical Associate Professor. He prescribed me Sumatriptan, and also found nothing wrong with my MRI.

5. 1 year ago, severe migraine recurred. I immediately took Sumatriptan, but it didn’t work. Repeat step 2. I paid $2000 HKD to see another neurologist, Professor YU Yuk Ling, an HKU Honorary Clinical Professor. I paid $10K HKD for a second Brain MRI + MR Angiogram. He prescribed me Rizatriptan, and found nothing wrong with my first and second MRIs. Note: this is the highest rank for ‘Honorary Teaching Staff’, and there’s only one other “Honorary Clinical Professor.”

6. Yesterday, another severe migraine! I immediately took Rizatriptan, but it didn’t work. Repeat step 2.

Now what? Do I keep experimenting with other triptans and exhaust the roster of HKU’s “Honorary Teaching Staff” by sampling another overpriced neurologist? As you can see, the severe migraine recurs once annually. Thus I don’t think I need Aimovig?