The reason I mentioned Super Glue is because it was invented by Eastman Kodak as a material to make optical gun sights but the stuff was too sticky to be useful.
When one of the scientists working on the project accidentally glued a set of refractometer prisms together, trashing several thousand dollars worth of lab equipment, they decided to abandon the project and, subsequently, they decided to market the stuff as "Kodak #910" because it took them 910 tries to perfect it before they gave up and repurposed the stuff.
Sorry, I didn't think about how runny Super Glue might be. I was only thinking of the optical qualities.
Regardless of the glue that's used, cyanoacrylate or otherwise, what do you think about building it up in thin layers to get the shape and thickness you want?