Unfortunately, it would be hard to find a cell battery this small. The original battery is 2" x 1 1/8" x 1/8". My samsung S3 battery is 2 1/2" x 2" x 3/16", so is far from fitting. If you were ok with shaving the molded battery holder down, you could probably fit one that's 2" x 1 1/2" x 1/4" or so (the thickness tolerance is hard to tell), but it would be a lot of work. I think I might just buy a speaker that has good battery reputation (i.e., NOT JBL).