I am working on a DC motor control project in which I need certain motor parameters such as torque constant, inertia, resistance, inductance etc (all constants needed to model and write DC motor equations).
Then there is no other option than trying to measure the parameters yourself. Resistance and inductance is fairly easy to measure (stall the motor and measure with multimeter/oscilloscope). K parameter is the second easiest to measure (or estimate), because it is directly proportional to the motor speed at unit voltage (steady state gain of the transfer function).
I would suggest (if you really need the parameters) that you try to measure the step response of the motor and figure out the transfer function. It should be a second order transfer function (attached).