Hi i just landed on your thread and went through the same issues with my TL494 SMPS. I had the same problem as you had hard to find IR2110 and wanted to go cheap. There is one possible way out, Gate Drive Transformer like silvio mentioned. You can get GDT cores from CFL lamps the small toroid ring inside. Do not use the EI transformer its used as an inductor. You will need an inductance meter to calculate the core AL value. In case one is not enough stick two together until you get enough AL. i wound mine as 1:1 turns ratio and targetted an inductance of 2mH. Building a highside BJT boostrapped mosfet driver is not easy. If you were attempting a discrete class D AMP you would have had more success there but going straight for a 220V smps with minimal circuit can be very challenging. This is just my two cents nothing prevents you from succeeding in the path you have taken. Your thread reminded me of the issues i went through with my first smps. Good luck on your venture and wish you best of success.