I just got a Fenix TK75 that uses four, I got about 30 batteries because I have about 8 different lights that use 18650's, and a higher quality charger that does discharge, charging, and refresh cycles.
On Amazon
Dulex makes a decent cheap battery, you can get 8 for $25 or 10 for $30
Foxnovo is a much better battery with internal protection circuits, four 2600's are about $28, four 3400's are about $56.
And I got a Opus BT C3400 charger because of what the reviews looked like from guys who have tried them all.
Get enough batteries that you can make two or three well matched sets for your light/s so that you can test and analyze their capacity. By matching the closest ones in sets and keeping them that way for use and charging these sets will last longer, run cooler, and go through way more charges. If you have one well matched set and another that has bigger differences in capacity and discharge rates the well matched set will last a lot longer. After a few use and charge cycles test the sets to make sure one isn't going south and goofing up the performance of the set.
Also if looking at Samsungs which are good protected batteries they come in an array of discharge amps, vaporizers need higher amps than lights do so stick to 3400 9 amp to 12 amp which are cheaper than the high 20a and 30a ones that you do not need.
If these batteries are used and charged right they hold a charge and last a lot longer. It's worth it to get one of the better chargers, they start at about $35