Insulating a MH lamp

Over the last 6 months I have searched high and low for a pre-fabricated metal halide lighting system with remote ballast which had between 250 - 400 W of light directed in a manor that would cover my 150 gallon tank.  After ordering and returning 2 such systems, I have decided to build my own remote ballast system and hood from scratch.

I have managed to locate all the electrical components I need, but need some help finding building materials.   I need to find a thermal insulator which I can place between the reflector and an Oak canopy (don't want my house to burn down).   I also need to find a relfector material from which I can form the parobolic light director.  Has anyone come accross anything fitting this description in their travels.

Feedback is Greatly Appreciated
Scott Corbeil