Help please - newbie

[Zaphodsk1]

I've got a mains powered 12v 50w single-bulb halogen lamp with dimmer that started buzzing despite trying several new (decent) bulbs and now seems to be dead. The transformer manufacturers in Taiwan aren't interested in responding. As it's expensive, can anyone advise on where to find transformers with integral dimmer switches for this type of purpose? I haven't been able to find anything at any of the websites referred to in threads on this forum. Appreciate any help, but please bear in mind I'm not in the trade and don't know all the terms!