Just buy some on amazon or from manufacturer’s website.
https://www.hylands.com/products/hylands-leg-cramps
This one is pure quinine, no other ingredients
https://www.vitaminshoppe.com/p/boiron-cinchona-officinalis-30c-80-pellets/bi-1088
Most homeopathic medicine uses an extraction/dilution method to keep levels from getting dangerous. I’ve been taking 4-6 of the Hylands every day for years to help with leg cramps…the anti viral properties are just a bonus. Oddly enough haven’t gotten cold/flu in years either.
https://www.nelsons.net/en-us/footer/homeopathic-dilution