[greenleafjacob]

You are best off buying a “USB condom”, a USB 2.0/3.0 connector with the data pins removed.

[MereInterest]

The problem there is that the USB standard requires the initial power transfer to be low amperage, and only switches to the high amperage mode on request, with the request being delivered over the data pins.

[jandrese]

USB condoms include a tiny chip that does the negotiation to get full power. Sometimes they even work better than the phone itself at getting the charger to give up the juice.

[theamk]

For up to 1 amp, three resistors is enough (that's how power banks work) -- and those easily fit inside the connector.

[Retric]

An actual USB condom should also include a surge suppressor.

However, the closest thing to that I have found is simple battery packs which can generally remove the need for 3rd party mid day charging.