Low voltage but relatively high current power supply?

Does anyone know where I could find a power supply that can output 4.5 volts (AC) at 2.5 amps? I'm getting a horn in the mail that takes 4.5VAC 2.5 amps but I haven't been able to find anything that has that high of a current at that low of a voltage.
Update: For those wondering what type of horn this is, this is an old vibratory fire alarm horn I got on Ebay.
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