Yes there are plenty of foods that are a good source of potassium, like bananas. Try the brand Naked, for juices that have lots of nutrients-no added sugar, many are a good source of potassium, just look at the nutrition label to see which have the most.
You're going to get a lot of responses for bananas on this one so get ready. There are a ton of different recipes for banana smoothies. Bananas are just by far the best source of potassium for you. Just be aware that too much just like everything else is not good for you, so watch it on the intake.