I got mine at Target for 19.99. It comes with two Lithium batteries (it's a good deal: they are $4 each)
You can find it cheaper if you look around.
The MiniUSB version is model No.: CEL2MUSB
Good luck.
REGULAR alkaline cells start working at ~1.5 volts and have ~2.2 amps of capacity. However, by the time 2.2 amps have been drained out of alkaline cells, the cell voltage has dropped (works like a ski slope) to ONLY 0.8 volts and this is the point the cell is technically DEAD.
Obviously, a battery manufacturer will sell MORE BATTERIES by making popular devices like flashlights that USE UP BATTERIES QUICKLY (like those 4 AA cell flashlights) so it is NO SURPRISE to find them marketing something that can ONLY USE L91 lithium batteries that sell at a premium price. Personally, I know to avoid these products as they ARE NOT ECONOMICAL and only add to inflated profits, and trash the environment with more garbage while claiming to offer SUPER CONVENIENT products.
If you must be tempted to use this (*really bogus) device to keep up your player/recorder/phone batteries, suggest instead of L91 Lithium, use Sony or Panasonic OXY-alkaline instead as these new batteries cost slightly more than regular akaline, BUT KEEP UP THEIR VOLTAGE starting at higher than alkaline 1.7 volts.
*PERSPECTIVE: While maybe not the ideal battery/charger for continuous recording purposes, the (L91) product's main purpose for which it's being marketed, is EMERGENCY POWER; 'ready to charge up a critically needed electronic device at a moments notice.' For this kind of use, it's a REALLY GOOD PRODUCT!
L91's operate fully -20 below freezing to extreme heated ambient temperatures. L91 batteries have AT LEAST 10 YEAR storage life at room temps, so even if stored for emergencies in (automobile) hot to freezing temperatures, they hold up (if stored new) in abusive coditions for many years ready to deliver full or nearly full capacity for that rare need.
So for occassional needs, it is NOT bogus to purchase and have ready.