You're looking for premade nishime? Nishime is actually a form of cooking known as waterless cooking. What you do is put 1 inch of water at the bottom of a sauce pan with a small piece of kombu, then layer veggies on top, bring to a boil and then simmer until all water is gone and veggies are very soft. Some veggie combinations are: carrot and bordock; burdock and lotus root; daikon and lotus root; carrot and parsnip; turnip and shiitake mushrooms; squash and onions. You can do more than just 3, I like to use daikon, parsnip, carrot, and squash. Just make sure you don't do just daikon and carrot or carrot and turnip because this can be weakening.
If you're looking for nishime premade it's going to be difficult. Sometimes they have at the asian markets in the refrigerated section but a lot of times they have added ingredients to it like fish broth :S In Whole Foods you can try to find premade ones in their grab and go japanese station. But I would highly recommend making it at home. You can premake it if you want, it lasts for 1 day in the fridge.
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