Parts such as the Speedometer - Tachometer: Bulb(12v3.4w,t10), Tachometer Assy, Cushion, Socket are included in the Gn250 1998 (w) (e02 E04 E22 E24 E25 E34 E39) Speedometer - Tachometer parts fiche.
On this parts fiche the Bulb(12v3.4w,t10) is the most specified component.