The specifications of the DSZH WK-6889 – temperature sensor do not give accuracy or type of the temperature sensors used.
They are most likely to be one of: RTD, thermocouple, or NTC thermistor.
A little testing reveals they are the latter (the cheapest and least accurate option). A thermocouple takes a long time for the cold junction compensation to aclimatise, the RTD would be a good choice, but more expensive.
The results of observing displayed temperature when accurate 90k and 20k resistors are substituted, and plugging them into Two point thermistor calibration follows.
The calculator explains the shortcomings of the simple thermistor model and the dependence of results on the temperature range chosen.
The device would seem to be a common R25=100k B=3950 NTC thermistor, mounted in a 4x30mm stainless steel tube, and on that basis, accuracy is probably about 1°C. These are widely used in 3D printers, and can be purchased online in a variety of mounts for a dollar or two.
The socket is a mini DIN 3 pin, thermistor is wired between pins 1 and 2.
If you have a Chinese digital manifold set without temperature sensors, this might be sufficient information to make a DIY pair of sensors.