It should be at the Magic Neep, that's where I got mine. You also have to buy a large pot at Tomes and Scrolls, it's all very expensive

It’s just that I don’t get the option to buy them

When I played I found it in Magic Neep and when I searched about it it says that was in Magic neep tio

Could be at dogweed and deathcap if not at the Magic Neep.

I’ve tried both shops in hogsmeade and it just hasn’t been an option :(

You might already have it then

If you already have the seed you need to buy the large pot in Tomes and Scrolls and then put it on the Room of Requeriment

I found it on accident in a dungeon