Protected 18650: http://www.banggood.com/4PCS-3_7V-2600mah-Lithium-Rechargeable-Protected-18650-Battery-For-Samsung-p-913785.html
unprotected 18650: http://www.banggood.com/4PCS-Samsung-INR18650-30Q-3000mAh-Unprotected-Button-Top-18650-Battery-p-1067185.html (for HIgh-Amps)
26650: LiitoKala 26650-50A 5000mah 26650 - great first impressions