I got some from my lfs but its a privately owned one and has harder to find items. It won't be sold at chain stores.
You could try buying it online which would probably save you money too. There's recipes to make it that you can find but that's another thing I haven't tried. Just be careful when feeding it. If you feed it to them for too long it can cause damage to their internal organs. I will have to get you a timeline for that on Monday when my lfs is open because I can't remember off the top of my head.