Come to think of it, I've got two batteries that you can have upstairs.

come to think of it 是一个固定短语，意思是"对了"、"现在想来"、"仔细一想"。常用作插入语，置于句首或句中，表示说话人突然想起某事，或者临时对自己刚说的话作进一步补充或修正。