The gear is part of Sony Minidisc MDM-3A mechanism – optical pickup KMS260A and KMS260E. It drives screw that positions the laser pickup. Sony part number A-3304-200-A.
Replacement and original gear
Replacement gear in the assembly
Replacement part was created using a semi-professional 3D printer using durable Nylon material. The gear was tested for correct operation.
You can find the gear here in schematics:
Sony MDS-JE500 schematic
Gear is compatible with following Sony Minidisc players: MDS-JE500, MDS-JE510, MDS-JE520, MDS-JE480. However, it might work also with other devices – just check your service manual.
The gear is available in e-shop. (plastic gear only, without the screw rod)