Hi Melissa. Although others raise some valid points on the proper and safe use of this piece of equipment, since your question only asks about the ‘purchase’ of kettlebells, I will answer based on the assumption that you already know how to, and feel comfortable using them. I purchased some of mine at Walmart. They were Gold’s gym brand and a bit cheaper than in other retail outlets.
Hi Melissa: Check out PerformBetter.com. They currently have a sale going on their ‘First Place Vinyl Coated Kettlebells, which are the ones I use with my clients. PowerSystems had a really nice 50% off sale that included free shipping about 2 weeks ago, but I think it may be over. Keep in mind that these are NOT competition KB’s so that handle size will vary with their weight. Best of luck!
Cap Barbell makes some decent, inexpensive fixed Kettlebells. You can find them on Amazon or Walmart (Website, ship to home/store). They’re pretty much bombproof, as most fixed iron or steel bells are, so I like to use them outdoors or when I’m teaching group classes.
Personally, I really like using Cap’s Adjustable Kettlebell; it adjusts from 20 to 40 pounds in 5 pound increments; currently (09/2013) find it same place as above for $150-$180ish. It’s shaped much like a competition kettlebell and remains the same shape regardless of weight. It also works great when training clients in their home as you don’t have to lug around multiples.