I have two of these that the brewery has never used case manuals batteries and adapters. They are $229 at co2meter.com . I'm selling them for $200 each or $380 if you buy both of them.

Measures: Carbon dioxide in PPM, temperature (F or C), % Relative Humidity
Sensing method: NDIR (Non-Dispersive Infrared)
Self-calibrating with fresh air
CO2 Measurement range: 0~9999 ppm (2001~9999 ppm over range)
CO2 Accuracy: ± 75ppm, ± 5% of reading (0~2,000 ppm)
Battery Life: approx. 24 hours continuous reading
Alarm: Yes (80dB)
120/220VAC adapter (power for long-term operation)
International Wall adapter kit
4 AA Batteries
ABS Plastic case