With 750 mAh, your scanner will run for about three hours. Why do you want less? You want MORE current-hours... 2300 mAh will run it for almost 16 hours.
Get the 2300s at a Wal Mart (cheap!) or a camera store or something... I bought some Quantaray 2800s with an ultra-fast charger. Works great.
And you want DOUBLE-A (AA), _NOT_ triple-A (AAA).