PostGIS Package for PostgreSQL 11 isn't Available

The package `postgresql-11-postgis-2.4` isn't available in the official PostgreSQL Apt Repository.

I've tried locating it when using both:

"deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg main 11"

"deb http://apt.postgresql.org/pub/repos/apt/ stretch-pgdg-testing main 11"

Neither has the package. This is causing the CircleCI Docker image build system to fail for those PostgreSQL images.

Anyway this can be added or is there a suggested alternative? Thank you.