I found a super cheap source of aluminum cased lifepo4 batteries, but I have not actually purchased them. I don't know enough about them to spot the red flags, but it looks super promising.
232.8US $ 3% OFF|16PCS 3.2V 280Ah lifepo4 battery DIY 12V 280AH Rechargeable battery for Electric car RV Solar Energy Golf Cart TAX FREE|Replacement Batteries| - AliExpress
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