Im thinking of replacing my black pearl 2 with this phone. Kinda FIL with mediatek proc

Anyway, where to get the replacement batt in the future ah? Since its not replaceable. I've had feeling im going to max it in 1 yr time and no im not gona replace phone. This phone will be my 2nd phone. Really usefull woh 2 sim. Especially for people like me which data network is on different sim