How to make Lithium medication from scratch

I take lithium carbonate as a medication. I was watching an "apocalypse-style" movie recently, which made me wonder how hard it would be to make my medication from scratch if I could no longer buy it. Some thoughts:

• I might be able to make it from batteries containing lithium, but in an apocalypse, those might be too valuable. Maybe there are other sources of recycled lithium.
• According to wikipedia, much of the world’s lithium comes from brine pools in South America. I currently live on the California coast. I assume we don’t have these…brine pools? Would it even be possible to obtain what I needed locally from natural sources?
• I have read that lithium carbonate breaks up in your blood, so maybe any form of lithium would work, not necessarily lithium carbonate.
• How would I figure out the dosage and the purity of my product? Lithium is well-known for its therapeutic level being close to its toxicity level.
• What kind of equipment would I need?
• How would I get my blood lithium level checks done to make sure I wasn’t overdosing?

NOTE:
I’m just curious. I’m not planning on actually abandoning my cheap store-bought meds for my amateur attempts at following a recipe I read online that could likely poison me.