Potassium is easy to get [1]. If you don't want to supplement with a vitamin/power, you can just eat a potato. Although that would go against 'keto diet'. I'm doing a IF (intermittent fasting) diet and I'm not restricted, so I could eat them if I wanted. IF is similar to keto, both put the body into a ketosis state.

[1] - All you need is one teaspoon a day. https://www.amazon.com/gp/product/B00ENSA93S/ref=oh_aui_sear...