My first question (and no doubt everyone else to) is WHY?
You will be adding a lot of extra weight to a valve. In carbon steel a 16" dick will weigh about 50 pounds. Depending on the type of valve and the orientation of the installation there could be added torque on the valve stem that would void the warranty.
They are made, we had some Al hand/valve wheels about 24" in diameter for use on gear operated valves. The primary purpose was to prevent the use of a valve wrench.
These wheels were cast aluminum with what could be called scalloped edges for gripping.
I'll try tomorrow to see who made them.
We also had some CI wheels that were solid except for about 4 lightening holes these also had scalloped edges. Again these were used to prevent using a valve wrench.
You might look at a hammer valve wheel as a lot of them are solid. All you would have to do is remove the hammer.
Masoneilan uses non-spoked handwheels on their valves but the diameters they use are much smaller. Still, the reason was to prevent the application of a cheater. They also have a tapered outer diameter so that the maintenance gorillas can't use a strap wrench on 'em.
This reminds me of a story from a valve company engineer who told us that they only make handwheels from soft iron. The reason was the ingenuity of plant operators to get a valve closed. He remembered one guy who was tried to force a leaky valve closed by puting on a cheater and a piece of scaffolding pole and them driving into it with a 1/2 ton truck.
your best bet is to fab it from some steel plate. Machine a the hub out of some round steel stock the cut a 16" diameter circle out of 1/2" plate or something. cut a hole in the middle and weld the new hub in the center.