Snape
You certainly don't have to work with me, but you certainly won't find anyone else who is both familiar with what's here and who is an expert on the magical fauna that you're looking for.
I'll head out tomorrow to hunt for aconite and see if there is Belladonna growing. I can't guarantee that I'll find it, because as a species it's not native to this part of the world. I have Ashwaghanda root growing, and it's doing quite well. The problem may end up being the mandrake root. I didn't have any in my bag -- I'd taken a shipment the day before I arrived here, and it isn't usually something I carry around with me. If I could get my hands on M. Officinarum, I could try to grow it in a box that's been infused with magic, but it's not native to this continent at all.
The others shouldn't be a problem. The plants, I mean. You're on your own with the Armdillo bile and the Tiger blood.