I took Fosamax for a few years for osteopenia. Then I went off it. A few years later when I was menopausal my bone density dropped. That's when I went on Prolia.

This is the kind of K-2 I use. My understanding is that the MK-7 form is better absorbed. I buy it either at Iherb or Amazon depending on who has the better deal.
https://www.iherb.com/pr/now-foods-mk-7-vitamin-k-2-100-mcg-120-veg-capsules/78992
I use this type of magnesium citrate, as that form is supposedly better absorbed:
https://www.iherb.com/pr/now-foods-magnesium-citrate-200-mg-250-tablets/691
Huge tablets but best value.

NOW foods has a good reputation for supplements. My internist likes them and they are quality assured. I always get them via mail order--easier and cheaper.

I hope talking with an endocrinologist will clarify the whole medication situation for you. I remember also feeling unsure about the whole thing at first. Took me three months to get a second opinion and do my research. Then I felt better about moving forward--I hope you do, too.