Gemini,
This is the product my wife uses:
https://www.papanature.com/store/Prod...&pid=LIF-40005
It's widely available online and at many health food stores.
The good thing about this product is that it contains well absorbed forms of both calcium and magnesium - it also provides a decent amount of vitamin D.
I advised my wife to take it after breakfast and dinner (or a snack) to improve the vitamin D absorption.
Be well,
HH