I don’t know of a car sold today that doesn’t have a 12 volt battery in it (unless you’re talking about hybrids- they’re a different story). Therefore, the differences among car batteries are physical size, capacity (cold cranking amps, for example), and connecting post style and orientation. There are adapters for post differences (side post to top post cables and vice versa). One can sometimes use a physically smaller battery than stock, but capacity is generally tied to size, and a smaller battery may not start a much larger engine than it’s made for.
There are brands of batteries that come with both side and top post connectivity. I think the several broad subsets of batteries that would satisfy your criteria are readily available. Just do a little research, open a store and stock the right ones.