You would need an inverter to go from USB-C Power Delivery's DC to AC to Apple's Magsafe 2 DC adapter. Going DC to AC and then from AC to DC is inefficient. Also, as far as I can tell, a USB-C PD inverter doesn't exist.
As a quick note: MacBooks with Thunderbolt 1 and 2 do not support charging via their Thunderbolt ports, only via Magsafe. Thunderbolt 3 supports USB-C Power Delivery and MacBooks with Thunderbolt 3 / USB-C ports charge exclusively through them.
Let's consider a new battery that has an AC outlet. RavPower makes a battery pack with an AC socket, but you are hard-pressed to get a single charge for a Magsafe-based laptop. Anker makes the PowerHouse 2, a $500 beast that could charge a recent MacBook Pro 13" about 6 times. (If The PowerHouse had USB-C PD ports, the number of MacBook recharges would certainly be higher, but wouldn't do you any good, as your Late-2013 MacBook Pro uses Magsafe.)
This is assuming that portability is key. If you are in a car (or have a 12V battery that you can clip into), a power inverter could be acceptable.