You can find all the replacement parts you need at Escapa.
Union CB-780 Headset Bearing 40.0x51.9x8 45/45
Features:
-Dimensions: 40.0x51.9x8 45°/45°
- Outer and inner rings: CrMo
- Balls: CrMo (HRC 61-66)
- Cage: Nylon
- Seals: LLU rubber (full Contact)
- Grease: Multemp SRL (Kyodo Yushi)
- Tolerance: ABEC-3