Children's Health Council doesn't specialize in gifted kids, but they are very experienced testing young children. If you talk to the intake coordinator and explain what you need, they should be able to provide you with a good fit. Both my kids were tested there (my son twice) and we had good experiences and got useful information each time.

I looked for someone who specializes in testing gifted kids, but I didn't find anyone suitable in my area. Maybe someone else has a recommendation?