OK, well, lots of foods contain potassium, even low carb foods. I don't know what particular type of diet you are seeking. Please see this link for potassium information:
http://www.livestrong.com/article/30...assium-levels/ You'll note there's a lot of fish options - as well as nuts/seeds for potassium. A good calcium source is salmon in the can - eating bones and all - or sardines in the can - bones and all. Many meats have potassium, as well as greens, bananas, yogurt etc.
Also see this link:
http://lowcarbdiets.about.com/od/nut...assiumfood.htm
Overall, if you eat heavy on a variety of veggies, you should get a good balance. As a warning, having an elevated potassium level could cause heart rhythm problems so don't oversupplement.