These cylindrical brushed DC gearmotors are available in a wide range of gear ratios and 6V & 0.04A with long-life carbon brushes (CB).
All geramotors have the same 16mm diameter body and 3mm diameter gearbox output shaft and 8mm shaft length, so it is generally easy to swap one version for another if your design requirements change (though the length of the gearbox tends to increase with the gear ratio).
Maximum rated torque is 2.8 Kg-cm @ 10 RPM.
Specifications