Fairly easy to find -- shop around:

However, check Didax first, as they offer a 20% discount to participants in this workshop.

pattern blocks

(available in wood or plastic.

Avoid the "foam" ones, because in my experience they are less accurately manufactured)

patty paper

plexiglas see-through mirrors (Mira, GeoMirrors, perhaps other brands)

Available from Nasco:

Geometry Labs template (template documentation: PDF)