Both 3DS Max and Bryce use a .MAT file for material presets.  3DS ones reference an outside map which is accessable, but the Bryce ones are kind of like a "roach motel" for textures (they come in but can never leave).  To the best of my knowledge, the only way to get those textures is to do a render in Bryce with the material applied on a plane.  But you might try the Bryce forum.