Call Kris at KC Services. This is something they could do pretty quickly. His number is 979.219.0503.
The problem is going to be getting the concrete truck. For a small job, wheelbarrowed to the back of the yard, concrete companies don't like their trucks sitting long and will tack on time charges for sitting on the job too long. You are only looking at about a cubic yard with a 4-4.5" thick slab. I'd price it both ways, with minimum truck delivery and time charges, vs doing it with bagged concrete.
A quick calculation shows you'd need about 30-80# bags of Sacrete Maximizer (lighter weight, larger coverage per bag). At $6.85 per bag (McCoys website), you'd be looking at $200 or so plus tax. Likely cheaper than a concrete truck, even through they are around $95/ yd, they'll likely not want a one yard job unless you have an installer that can pull strings or sets up a few small jobs per day.