Justin's Suggested Radio Battery 2S 6200mah
This 2S 6200mAh pack is the one I recommend for the TX16S MK3 because it lasts a long time—I charge it the least out of all my radios. You will need a LiPo charger, but the MK3 also adds built-in balance charging, which is a really nice upgrade.
You'll be taken to Tinyurl to complete your purchase.