Identify uncommon thermistor
That looks like a Pt1000 resistor. These are platinum resistors with a resistance of 1000 Ω at 0°C and a postive temperature coefficient of resistance with temperature.
Have a look at the resistance ratio chart. This one by Kongsberg shows the resistances for a Pt100. Scale by 10 for a Pt1000.
Temperature    Your reading   Table
 25°C          1100 Ω         1097.3 Ω
100°C          1340 Ω         1385.1 Ω

Pop it back in the kettle (at sea level) and measure the resistance again to check.

Pure platinum has α = 0.003925 Ω/(Ω·°C) in the 0 to 100 °C range and is used in the construction of laboratory-grade RTDs. Conversely, two widely recognized standards for industrial RTDs IEC 60751 and ASTM E-1137 specify α = 0.00385 Ω/(Ω·°C).
Before these standards were widely adopted, several different α values were used. It is still possible to find older probes that are made with platinum that have α = 0.003916 Ω/(Ω·°C) and 0.003902 Ω/(Ω·°C). Source: Wikipedia's Resistance thermometer.

There are very many manufacturers and several can make to order with case and lead lengths to suit.
I note that yours has only two wires. For industrial applications where the sensor may be remote from the amplifier a three or four-wire connection is made to allow correction for voltage drop along the current-carrying wires. Since yours does not have these additional wires it is probably located close enough to the measuring circuit that the error produced is not significant.