Foods generally don't contain large amounts of potassium citrate itself in the same form as the prescription/supplement. Instead, many fruits and vegetables provide potassium plus citrate/citric acid or other alkali precursors, which can support higher urinary citrate.
For kidney-stone prevention, some particularly useful choices are:
Food Why it may help
๐ Lemon / lemon juice Very high in citrate/citric acid; one of the best-studied dietary sources
๐๐ฉ Lime High in citrate
๐ Orange / orange juice Provides both potassium and citrate
๐ Grapefruit Contains citrate and potassium*
๐ Melons Good potassium source and high water content
๐ฅ Avocado Very high potassium, but not especially high in citrate
๐ฅ Potato High potassium
๐ Banana Good potassium source
๐ฅ Kiwi Potassium plus organic acids
๐ Tomato Potassium and high water content
๐ฅฌ Leafy vegetables Potassium and dietary alkali
Lemon is especially interesting for calcium-stone prevention because of its citrate content. Human studies have shown that lemon juice/lemonade can increase urinary citrate in at least some people with low urinary citrate.
One important distinction: eating a banana or potato gives you potassium, but that's not equivalent to taking potassium citrate. Prescription potassium citrate delivers potassium specifically combined with citrate and produces a more predictable effect on urinary citrate and urine pH.
For someone who forms calcium oxalate stones, a practical dietary approach is usually plenty of water + citrus (especially lemon) + normal dietary calcium + lower sodium, rather than simply trying to eat the highest-potassium foods.
* Grapefruit can interact with several medications, so it isn't appropriate for everyone.