1kHz AC from mains power
Just an idea and not the conventional approach I'll admit. How about using an off the shelf (cheap) audio amplifier driving a step up transformer (reversed audio output type 1:10 ratio - 10V in gives 100V out) instead of the speaker and a 1kHz sine wave generator as input. 



The output would be isolated from the mains. The 'volume' control could be used to give a 'variable voltage' output and the sine wave generator frequency could be varied if required.