They serve it all the time - all locations, I believe.
In addition, the Uno's franchise started selling GF pizza last month. They sell it at all locations except the original two downtown.
One more option, Aurelio's has GF pizza. All but one store, however, buy marginal crusts from a vendor. The one in Addison makes their own crust and it tastes decent.
So, between them, hopefully one will be close to this child's home.