You Do Need power plug adapter while traveling from Brunei to Mauritius.

Here is Why You Need An Adapter

The outlet and plug type used in Mauritius are C and G and in Brunei is G. This is how they look like.

Brunei

In Brunei, outlets of type G are in use.

Type G

Mauritius

In Mauritius, outlets of type C and G are in use.

Type C

Type G