Kirk sent me this pic of Smith Metalworks Roundhouse and Turntable.
Here is the info Kirk sent me:
The green base of the turntable is 33.75" and the track and rotating red portion are 29.75". Better than a Lionel turntable and roundhouse, but still a little skimpy for Standard Gauge steam locos. A version large enough for the Hiawatha would be a great product!"