Re: 18650B compatible?
You should give us some more information, because there are too many 18650 flashlights. Take a look at the big companies homepages like Fenix, Olight, Sunwayman to name only a few.
If you have a smaller budget (less as $30), you should take a look at the Hong Kong shops (a few brands have a good quality like Convoy). Of course you can buy a cheap $7 flashlight within shipping on ebay, but often the quality is really cheesy.