Duracell Inc., an American manufacturing company owned by Berkshire Hathaway that produces batteries, now offers replacement camera batteries for the most popular DSLR and mirrorless camera brands.
A Duracell replacement camera battery fits Canon EOS 5D, 5D Mark II, 5D Mark III, 5D Mark IV, 5DS, 5DS R, 6D, 7D, 60D, 60Da, 70D, 80D, etc.
https://www.duracelldirect.com/digital-camera/canon/eos-6d-mk-ii-battery-adapter-charger.html