I got 10 flyback transformers on eBay for $25.00.
https://www.ebay.com.au/sch/i.html?...former.TRS0&_nkw=Flyback+Transformer&_sacat=0

You can get them from old TV sets or from a TV repair shop.
If you are not committed to the ignition coil, this is a great way to go.
Here is the entire circuit. Except that I also put a 2 ohm 10 watt resistor on the positive supply wire for less abuse on the transistor.
You have to pay attention to the direction you wind the solid wire on the armature of the flyback or it won't work. Like the color picture. If it doesn't work just swap the wires on the feedback windings or rewind it the other direction.
This self oscillates and keeps making 3/8" sparks at a fairly high frequency.
I have made a few of these for a Jacobs Ladder and other projects.

That is thousands of volts and can be lethal.
DON'T LET IT BITE YOU!

View attachment 155025
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There are about 10 pins on the bottom of the flyback. When you get it working, hold the positive wire near those pins. Sparks will jump to the negative terminal. Solder your negative wire to that terminal, clip all the rest and cover them all with clear silicone glue.

Here is a video.

You do need a heat sink to keep the transistor cool. Don't let it touch anything but the transistor.

The 3055 is just barely adequate for audio - a TV flyback transformer won't do well going that low. The FBT is also part of a resonant system that includes the scan yoke, so you'll have to find out what frequency the bare component is happy with anyway. My thinking is; you'll need to find something with more turns on the windings. The chopper transformer from a bipolar transistor blocking oscillator PSU is a much better option. The existing HV transistor will be fast enough, but a high current low voltage type would be better for driving one of the LV windings - might be worth seeking out a low VCEsat type.

 

The 3055 is just barely adequate for audio - a TV flyback transformer won't do well going that low. The FBT is also part of a resonant system that includes the scan yoke, so you'll have to find out what frequency the bare component is happy with anyway. My thinking is; you'll need to find something with more turns on the windings. The chopper transformer from a bipolar transistor blocking oscillator PSU is a much better option. The existing HV transistor will be fast enough, but a high current low voltage type would be better for driving one of the LV windings - might be worth seeking out a low VCEsat type.

Thanks for the advice