I went to Walmart first because Consumer Reports rates their batteries highly and they have the best warranty, but they only had their cheapest and most expensive batteries. The battery monkey, who had never heard of Interstate, only being familiar with the Sam's Choice of batteries, said that she didn't have any way of knowing what the nearest store had in-stock.
My phone showed what they had in-stock!
Not the battery I wanted...
I ran home, grabbed my cordless screwdriver, and went to AutoZone. Their manager price-matched Walmart.com's $88 battery! AutoZone charges $150 for a comparable one!
The only issue was the battery terminal seemed smaller than the old one. Mom's clamp seemed to have stretched. I sacrificed a shim from my Civic, which didn't squish very well for the new battery.
I used a hose clamp to return the shim back to its original shape and a 3/4" socket to tap the clamp all of the way down.
It's tight!