You can purchase nearly all of these items in Celadon City. You need to progress through the story of Pokemon Let’s Go until you reach Lavender Town. Visit the Pokemon Tower in Lavender Town to fight your rival then you must travel West to Celadon City. Once there, check the huge superstore in the area. Head to the 4th Floor, Wiseman Gifts. The only one you cannot purchase here is the Moon Stone, which you can find in Mount Moon. They cost 5,000 Pokédollars each from the store but you can purchase as many as you need.
If you are talking about Mega Stones, you should of put "Maga Stones" in the title. Here's a video on how to get every Mega Stone.