Anker is a good brand but I have another lesser brand know that I don't have with me right now, so unsure of brand, that I got on
Amazon for around 8 dollars as part of a lightening deal, it works fine and is one of those smaller ones. Large capacity ones that are much heavier and cost around 30 and up. My daughter uses her phone alot and would use a small one twice a day but if you don't use your phone too much you could probably get by with just a small capacity bank. There are many versions depending on how much charging capacity you want. I would check Amazon and see the rating. Some products have fake ratings so you can see if a particular item has a few to many on fakespot dot com.