Hi,
your bulb is a standard 20watt which is used in many light fittings.
if you go to any bulb shop or arehouse inc B&Q then you can get them off the shelf.
if you speak to anyone at the shop just take the bulb in, it is used in many kitchen underpelmet lights but sometimes they are 10W so specify 20W, it is also used in many bathroom mirror lights, halogen lights in kitchen extractors etc etc,
regards,
John.