Oh, dude, don't buy raita - it's super easy to make.
All raita starts with plain yogurt, so get a tub of that. After that, there are a few variations, and room for experimentation:
For the most basic North Indian-style chunky raita, dice (or grate) some cucumber, mix it into yogurt, add salt & pepper to taste. If you want it to be more aromatic and you've got some cumin, toast it in a pan, grind it up, and mix it in. If you want it to have a bit more kick, mix in a bit of red chile powder. You can also chop up some tomato and mix that in, if that's your thing.
For the most basic Pakistani-style raita (the awesome green stuff that is often served with kebabs), this can be made in 30 seconds by mixing yogurt with green chutney. To make a quick green chutney (which takes 5 minutes), throw a bunch of cilantro, a wad of mint leaves, some chopped green chile, salt, pepper, some lemon juice, and a bit of cumin into a blender and run it until it's a mostly-smooth paste (amounts all vary according to taste).
Another option is dahi boondi (which translates to "yogurt boondi"), which is essentially a chunky raita made with little fried bits of batter instead of veggies. You can buy bags of boondi at any Indian grocery store. Once you get them, either stir them right into slightly-watered-down yogurt with salt, pepper, ground cumin, and red chile powder, and you'll get a cool, slightly-soggy, slightly-crunchy raita (this is the way I like dahi boondi). Optionally, you can get all North Indian-style authentic on it by soaking the boondi in cold water until they soften up, then straining them out, squeezing out the excess water, then stirring them in. Or you can soften them up South Indian-style by replacing the soaking water with very diluted yogurt or buttermilk (my Tamil wife swears by this, and scoffs at the water-soaking method).
Whatever kind of raita you decide to make, there's absolutely no cooking required.