We recommend using any charger that can handle the capacity of the battery- We recommend charging at 1C, so you will need to make sure that you get a lipo charger capable of charging at a 1.8A rate at 4s.
Some excellent options are:
(easy a/c charging- plug directly into the wall)
The TBS B6AC Charger: https://quadquestions.com/product/tbs-b6ac-battery-charger-with-integrated-power-supply/
The Accucel 80W (requires an external power supply or car battery)
I hope that helps.