Bellerin There are some general supplements that are helpful for us Hypos, then there are specific supplements which should only be taken if tested and found deficient.
OPTIONAL TESTING but don't supplement unless known to be deficient:
Selenium (helps conversion of T4 to T3 and helps lower antibodies where Hashi's is present)
Mineral Complex (choose one that doesn't contain iron as it stops everything else from working, nor iodine nor calcium). If it contains selenium you won't need to supplement selenium unless the amount is very small.
Probiotics are good for gut health
Co-enzyme Q10 can be a good idea, supposed to help with fatigue amongst other things
Most people are low in magnesium
Cytoplan (Nature's Own is same company)
Lambert's (Nature's Best is same company)
Doctors Best D3 is excellent
I like some NOW Foods products
Some you can get from Amazon, I also use Bodykind, Big Vits, Health Monthly, Lifestyle Labs, Cytoplan you can order direct, also Biocare, you need to compare prices.