The materials used in the project can be found on the following website:
Betzold 

Equilateral felt triangles (in orange, red and green, with sides measuring 5 cms.) can be ordered from:

Rittel-Verlag
Frank Rittel
Meldorfer Str. 11 b
20251 Hamburg
Tel.: 040-414 253 16
www.rittel-verlag.de

Equilateral wooden triangles (in yellow, orange and light green, with sides measuring 5 cms.) can be purchased from: 

Erzgebirgische Holzspielwaren Ebert GmbH
Sorgauer Str. 1
09526 Olbernhau
www.holzspiel-ebert.de