Synthesizer power supply

I am encountering difficulty locating a transformer for my synthesizer. 120 Volts 11 watts consumption. The PSU consisted of a transformer with 20-0-20 and 8 volt. 5 secondary leads in total. The board had two rectifiers, one feeding 7915, 7815. The other rectifier feeding 7805. Where could I scavenge a similar transformer or should I try to create from 16 VAC wall wart? How do I get the separate 5 VDC from that type of PSU?
Thanks