I would like to suggest the motor SY42STH38-0406A or SY42STH38-0406B (double shaft), it would be good for projects that need high torque at low speed, and would cause less heat because of the low current (0.4A/Phase).
Specifications:
Hello.
Thank you for your suggestion. It might be helpful for people who are looking for that kind of low speed, low current, high torque stepper motor.
-Brandon