To buy nootropics legally using bitcoin you can check out the link to the website below.
https://nootropics.com/btc-guide/
That website tells you in a step by step guide on how to legally and easily buy newtropics with bitcoin online.
Here's another website where you can purchase nootropics online safely and legally.
Not sure if they accept bitcoin or not but they do accept credit and debit cards.
You could get a prepaid debit card then buy the nootropics through them that way.