No, actually, Mini UPS are available for 1.8-2.3k, which have the 12v output and input, you just have to plug ur adapter into the powerbank and plug from the powerbank to the ONT or router, you do not need to remove it ever because it switches on its own. Here is the links:You mean a powerbank? but then that powerbank would need to be unplugged & charged mostly after 1-2 days, isn't it?
Zinq Tech. 12v