I know this is an old question but I found a solution that might help for those with a similar dilemma. MacBooks with USB-C can take in power from most any USB charger of 12 watts or more. This means a USB charger that comes with most new iPads, iPhones, or most any personal computing devices lately will provide power to a MacBook. Just be aware that 12 watts is the maximum USB-A can provide. In my experience most USB-A chargers are limited to 5 watts so read the specs carefully if you want power. It won't hurt the charger if try though, if it's a 5 watt USB charger the MacBook will simply refuse to draw power... and your battery will continue to drain.
A 12 watt power supply isn't likely to keep your MacBook running indefinitely, but it will slow down the rate at which the battery drains. If the MacBook is shutdown or put to sleep then 12 watts can possibly get a dead MacBook back to full charge overnight.
With a light work load a 27 watt USB-C charger could keep a MacBook running indefinitely. 27 watt USB-C chargers are commonly included with tablet computers and the like (at least in my experience), and seen as a common rated output for 12 volt automotive USB-C chargers. This 27 watts is from 9 volts at 3 amps. 9 volts is simple to regulate down from a 12 volt automotive accessory outlet, and 9 volts is a standard voltage output under the USB-C specification. 3 amps is the maximum current most USB-C cables can handle. This makes 27 watt USB-C chargers relatively cheap, and therefore relatively popular.
Oh, and ThunderBolt 1 and 2, like mini-DisplayPort which it shares a connector, does provide power from the port. The power is not much, less than 10 watts, and not enough to do much more than provide power needed for active cables and adapters. In fact some active adapters require more power than Thunderbolt can provide. If you have a computer with Thunderbolt 2 port then plug your MacBook into a free USB-A port on the computer to charge your MacBook. If it's new enough to have ThunderBolt 2 then it's new enough to provide 12 watts from a USB-A port.
This is assuming you have the right cable to plug your MacBook into whatever USB port you found to provide power, so even if you find a charger you might also need to find a cable.