You may buy direct from any of the following fine companies:

Campbell Scientific Inc, Utah, USA, www.campbellsci.com/
The world leader in dataloggers, sensors and accessories
Area:  USA and Worldwide
Contact:  Mike Thurgood

Geokon Inc, New Hampshire, USA, www.geokon.com/
The world leader in vibrating wire technology
Area:  USA and Worldwide
Contact:  Tony Simmonds

Campbell Scientific Ldt, www.campbellsci.co.uk/
The European subsidiary of Campbell Scientific, Inc. of Utah, USA and serve the whole of Europe through it's head office in the UK, through affiliated offices in France, Germany and Spain and via a network of distributors across Europe.
Area:   Europa
Contact:  Simon Dawe

GEONOR, Inc., P.O. Box 903, Milford, PA 18337, USA, www.geonor.com/
Serving users in Geotechnical & Structural Engineering, and Meteorology.
Area: USA, Canada, Hispano America (Not Brazil)
Contact: Ed Brylawski, P.E.

Itas, Aas, Norway, www.it-as.no/
IT Consultant, instrumentation, service provider and datalogger networks
Area:  Norway
Contact:  Oddvar Haga

Intermountain Environmental, Utah, USA, www.inmtn.com/
Environmental equipment and services
Area:  USA
Contact:  Josh Hanks

Koenders Instruments B.V., Almere, Nederland, www.koenders-instruments.com/
Instrumentation for hydrology, meteorology and geotechnical systems, datalogger networks
Area:  Nederlands
Contact:  Robert van der Veen