Transformers work with AC signals, preferably the sinewave kind, and when you step up the voltage the current steps down by the same ratio. If this was not the case then you would have the possibility of getting more power out than you put in. The problem with squarewaves and transformers is that you may experience severe signal distortion and core saturation depending on the current levels which I don't think you have been very precise about. Transformers are also difficult to work with at higher than audio frequencies.

The 1:3 turns ratio will get you about 90 VPP which is just a bit short of your requirements.

 

There is another idea.
12Vdc Power + NE555 boost → Full wave rectifier + Caps Filters → 120Vdc → LM317HV(+), LM337HV(-) → +50Vdc, 0V, -50Vdc.

 

These transformers are meant for use at high frequencies (their L is very low) and cannot be used at 15-500Hz, the frequencies mentioned.

 

Does anyone know where i can purchase a 1:10 turn step up transformer that can be mounted on a PCB please?

Thanks!