There is a commercial unit that does this but I consider it and anything similar to be potentially dangerous.
Stereo amplifiers are designed to produce power which is not wanted and can electrocute anyone using it. Also, there is a significant frequency roll off in these power amplifiers so that you end up with only a couple of harmonics above 30 kHz at the most. You really need to get over 20 harmonics at 2.5 kHz in order to achieve reasonable effectiveness.
Observe the signal with a scope and you will see junk.
>- $10 zapper rather than take the hours to round up the parts and build it,
The $10 zapper is much better but will not match the 555 version in capability.