You can install Microsoft's natural voices, which will be able to work offline. After installation, the voices will be available in any application that uses SAPI 5 (for example, in the Balabolka application).

English (United States) voices:
 
- Microsoft Aria Native (female)
- Microsoft Eric Native (male)
- Microsoft Guy Native (male)
- Microsoft Jenny Native (female)
- Microsoft Michelle Native (female)

Official website of the Balabolka application:
https://www.cross-plus-a.com/balabolka.htm
