You guys thought about try a lighting and Sound/Audio visual suppliers

ie:
in Sydney... Grafton Sound and Lighting, Bourke street and Panovision is another. These guys supplies television studios and film sets. You should find a variety of flocking materials they use on sets. One variety I'm thinking of using when I retube my newt is a flat/matt black foil. All designed to absorb reflections or darkening off areas of a stage. Even give the Sydney theatre companies set department a call they could probably help you on a supplier.

I used to work in the industry and used this stuff fairly regularly. Although having never personally brought it I do remember it can be fairly expensive.

Just my thoughts

regards