I hope to measure the temperature of stamen and stigma on a living flower in the wild. It will be the best if I can do it without touching the flower. If a IR-thermometer is a choice, which model you might use for such purpose (very small object)?
Measuring temperature of small objects is very challenging. Have you considered measuring the air temperature around those? In food system, for example for shell eggs, we use air temperature in the immediate envirionment, because we cannot put probes into every egg.
Yes, measuring the temperature of small objects is challenging. I have not discovered an IR thermometer with a small enough target area for your task. Although it would not be entirely satisfactory, I would probably use gentle contact with a very fine thermocouple. You may have to make the thermocouple yourself if you cannot buy a fine enough one.