Mercedes W203 C220 CDI OM611 Thermostat fault, effects of a faulty thermostat

Mercedes C220 CDI OM611 Thermostat fault. Thermostat leak causing low engine temperatures. Reduced efficiency and power. Hard to find part. Australia mercedes had none and they wanted $200 plus shipping OEM part not through mercedes. BEHR TH1392 92C Www.benzperformanceparts.com.au