Well I was thinking the same. Here is was possible way of doing it:
Using my 1 battery setup with step up circuit. Run direct connection of 9 volts to the 555 zapper circuit, then run the 33v to Beck's 358 input. Join the outputs of the of both together.
So this is what it would look like:
positive output on beck side = about +32V
negative output of beck side = about -32V
reversal happens at 4Hz intervals.
zapper output on 555 side = about +8V,+.5V,+8V,+.5V frequency dependent.
lets do the math: +32V +8V = +40V, +32V +.5V = +32.5V
-32V +8V = -24V, -32V +.5V = -31.5V
40V could be packing bit of juice - output control should be used or using only the 25V output from the step up circuit.
now we need to use some diodes to prevent current leaking in to either chip.
I'm not an expert so the only way to find out if this works is to build one!
For me I have to keep this experiment till the cooler days of the year. Construction project on my house cannot wait.