Hi
Futronix make a P50 single circuit dimmer that can be used with mains voltage lamps or magnetic (wire wound) transformers. This is rated at 600W.
They also do a P100 which is two circuits at 300W (mains voltage lamps or LV (electronic or magnetic transformers))
You can also buy basic remote/touch dimmers such as Varilight from B&Q that may suit your application and cost range better. Check the loading in watts and the transformer compatibility.
check Futronix out at
www.futronix.com and B&Q at
www.diy.com