Based on this product's specifications, here are some alternatives and similar models
O2 sensor for testo combustion analyzers, model 327-1 / 330-1 LO2
Summary description:
O2 sensor compatible with testo combustion analyzers, designed for models 327-1 and 330-1 (LO2). Provides accurate oxygen measurement in flue gases for combustion analysis, burner tuning and emissions checks. Intended as a replacement or spare part to restore analyzer functionality and ensure reliable gas measurement during maintenance and inspections.