Yep, I'd check Costco (or maybe Wally World)
At least Group 27 size.....I'm thinking about $75 each. This is the size that completely fills one of those common battery boxes.
I wouldn't mess with the smaller group 24 size for your application.

Johnson Controls makes many of the common brands you'll see.
Look at specs, warranty, weight. Heavier is generally better, unfortunately.