Hey @Cosmo,
Do you still the theme files available? Could you share it with us? I will upload them to some persistent cloud and put them into this thread.
The best way to upload a theme tk the persistent cloud ks the GitHub repository for InvoicePlane themes GitHub - InvoicePlane/InvoicePlane-Themes: The official InvoicePlane Themes repository.
That way, at some point with new versions thd theme will be in the .zip of the releases