Supporting a motor shaft with a bearing on the opposite side greatly increases the loads the motor can support.

Size: 3mm ID x 6mm OD x 2.5mm width
Weight: 0.5 grams each
Double shielded for extended life.
Chrome steel construction.  Shielded.

Don't have a 6mm drill bit?  You can use a 7/32" bit and ream the hole out slightly to press a bearing in.