Would you be picking up yourself or needing delivery?
Western Concrete and Alternative Landscaping are both good to deal with. Western is a few bucks cheaper per yard. You can drive in with a shovel and a few buckets or a truck and be on your way pretty easily. If it's a smaller load that you need delivered though, Alternative could work out a little cheaper for delivery.
You've probably already done some research on what's best for the job, but curious if you'd considered landscape fabric (not the cheap stuff but the good contractor grade)?