Just got Digiland 7" Tablet as gift, is there a battery I can buy to carry to hook up externally if installed battery runs low?

Received this 1st tablet as gift and love it so far, is as fast as my laptop and have been able to do all I do with it just fine. Only thing box states battery power as only three hours so wondering if there is battery I can buy to carry with me that I can plug in on outside where has plug ins incase the one inside tablet runs low... is there such a thing?