What's an alternative to those dubious high voltage generators from Amazon?

[Devil Master]

My project is to build an ion generator. The theory states the following:
1) a battery powers an oscillator, which generates an AC signal
2) the output of the oscillator is fed to a transformer which increases the voltage
3) the output of the transformer is fed to a Cockcroft-Walton multiplier, which increases the voltage even more, and turns the AC back to DC

The multiplier is a simple concept, so I don't need help for that.
If I chose a high voltage generator from Amazon as the input for the multiplier, I would not have the guarantee that it works as advertised, since those sellers always inflate the specs, so I would like some guidance to build something similar myself.

For the oscillator, I looked at the 555 timer, and designed a circuit that generates a 72 Hz square wave signal with a duty cycle of 50% (see attachment).
Now I have a problem. Even though it technically "alternates", that's not what is commonly meant with AC. I need a sine wave that goes from a positive voltage to an equal negative voltage and back again, so the transformer can work correctly. How to I turn a square wave signal into a sine wave signal?

[MRMILSTAR]

You can look at what I made for my CW multiplier. It consists of two AC flybacks in parallel driven by a ZVS driver. The ZVS driver was obtained through E-Bay and is very common. I also got the AC flybacks from E-Bay. They are less common.
https://highvoltageforum.net/index.php?topic=1524.0

[FPS]

For the oscillator, I looked at the 555 timer, and designed a circuit that generates a 72 Hz square wave signal with a duty cycle of 50%

Note that is a really low frequency to operate a CW multiplier and would require about 1uF of capacitance per stage, even with let's say a modest 5kV input it would be huge and expensive. For a better visual look at the size of a 2kV microwave doubler capacitor at 60Hz. The small ferrite core transformers I assume you are looking at will better operate in the 20kHz range.

Your CW multiplier will still work with pulsed DC as opposed to AC sine wave but you can also buy square wave alternating -+ modules like so https://www.aliexpress.com/item/1005004977783673.html?spm=a2g0o.order_detail.order_detail_item.5.1b7ff19crJk8B4 if you want sine wave AC its easiest to use the ZVS drivers like Milstar suggested.