Maybe something like this but honestly youre probably better off just replacing the heater with the correct heater

https://www.amazon.com/VEVOR-Voltage-Converter-Transformer-5000W/dp/B0B5R2426Y/ref=mp_s_a_1_29_sspa?keywords=120v+to+240v+step+up+transformer&qid=1686340641&sr=8-29-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExNTcyS1AxRVY2OE1VJmVuY3J5cHRlZElkPUEwNDA0MTMxRDdQRllXR05NNzFYJmVuY3J5cHRlZEFkSWQ9QTA4MTcyNjYyVzlWNjY5U0ZQR1A0JndpZGdldE5hbWU9c3BfcGhvbmVfc2VhcmNoX2F0Zl9uZXh0JmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==