Hello Anita,
You won't get sewtric motors anymore, you will need to change the motor and control, you buy the motor with control complete from any sewing machine shop or on line from www.sewingonline.co.uk/instructions, the model you want is called YDK, that is the standard make, if you have a light fitted to your machine it is very easy to wire in the two wires.
Ken
drivewithken at blueyonder dot co dot uk, December 2009