The 124 and 201 gasoline engines use a Group 48 battery as OE, but a Group 26R will fit perfectly and has plenty of cranking power eventhough it is several pounds lighter that the OE Group 48. The 26R is a common size and the type sold by Costco, Pep Boys, and Autozone are all identical and manufactured by Johnson Controls. They cost about $40 and have about a four year warranty, but last seven to ten years in the mild So Cal Climate I live in. If you peel off the stick on labels, they become unobtrusive plain black batteries.
A modern medium priced 26R is about 525 CCA. The OE Group 48 was 495.