The Free & Clear Dishwasher Detergent is available in 45 oz. and 75 oz. packages, with prices ranging from around $5.00 for the smaller package and about $8.00 for the larger size. You can find the detergent at most mainstream and natural food stores or online.
When I first started using the powdered Seventh Generation Automatic Dishwasher Detergent, I felt it did a great job of getting my dishes clean. However, after a while I noticed a couple minor problems. A film would sometimes be left on my glassware and/or some detergent would be left undissolved in the dispenser after the washing cycle was completed. These problems didn't really bother me until, quite by accident, I switched detergents for a while.
For about a week, while I was out of Seventh Generation, I used a mainstream dishwasher detergent. Boy, were my dishes clean! As much as I wanted to believe that my natural brand cleaned as well as a brand that wasn't so eco-friendly, I found quite a discrepancy. My glassware sparkled. The old coffee stains in my mugs were gone.
I won't switch to consistently using a conventional dishwasher detergent, though. Phosphates, which can harm water life, are still used in most big brand dishwasher detergents.
I'm going to try Seventh Generation's liquid detergent in hopes that the issues I have with the powered detergent will be solved. Although I know that buying the gel detergent will come with a larger carbon footprint associated with the packaging and transportation of the product, it will help keep phosphates out of the water system.