to make a cheap one get a 555 timer and configure it in an astable mode. for a better frequency stability generate about 100hz or 120hz and divide it by using a JK type or a Dtype flipflop to divide the it to two 50hz or 60hz two banks. then you will have to wave one inverted and the other not inverted. using transistor one or two for each bank usually an NPN (BC547 or SL 100) for amplification may be in darlignton mode or emitter follower. then for driving the transformer you will need two banks of power fets or transistors 2n3055 or TIP 142 or IRF250 (get their datasheet for their connection) connect collector or the drain of the power tansistors or fets to the transformer. the transformer should be of 12v -ov - 12v secondary side and primary 110 or 220v more or less power should depend on the load to serve and your judgement. experiment with this first and lets hear your feedback.
PLS IF YOU HAVE NO PRIOR KNOWLEDGE OF ELECTRICAL POWER PLS DONT ATTEMPT TO DO THIS HAS HIGH VOLTAGE IS INVOLVED. PUT SAFETY FIRST