It's a Group 47 or H5 battery form factor, with AGM chemistry. Gen 1 and Gen 2 use the same ones. Not the most common, but common enough that most manufacturers make it in at least some of their product lines. You absolutely can get them through CostCo, but it may take a phone call to assure stock or have one ordered for your favorite location.The 12V batt looks to have a bit unusual dimensions and recessed terminals and I have to assume it isn't a generic product found at Costco, etc. The batt looks very clean, uncorroded and unswollen. This car only has 9k miles on it. I got it from an Oahu dealership at the first of the year. It had 1k miles on it from the dealership, who told me the dealership manager was driving it once in a while.