When it comes to focal items, those would most likely be quested for from a high level mage NPC or taken as loot from some high level MOB. As for reagents, those would be bought at most any spell research vender.
On an on topic note.
When you thing of herblaw, I call it herbalism, think not of magic but of medications and such. Herbs can give energy, increase mind development, and can be used in healing so don\'t think in lines of casting a spell from a potion.
Now when it comes alchemy(sp) you can thing of magic. Actually alchemi is a science to equal magic. This would be taking elements and trying to alter them to cause different results, IE turning lead to gold. Since this would have to be edited for game purposses, think of it more as a potion you could put on your armor to make it stronger, sprout spikes, and so on. Even aplied to skin could have effects.
So think of alchemi as something to ajust the melecular aspect of what ever it is applied to. Think of herbalism as something to use to boost natural abilities, heal, and cure. So basicly herblaw makes medication and vitamins and alchemy makes things that are a small type of chemical magic.