Arduino board Library for STM32F427 / 437

Please tell me where can I find Arduino IDE  board Library for STM32F427 / 437 core?

It is not listed here GitHub - stm32duino/Arduino_Core_STM32: STM32 core support for Arduino which is the site which ST Microsystems sponsors for Arduino developments.

The page above also links to instructions for adding new boards types. You could also try a enquiry on the associated forum: https://www.stm32duino.com/index.php