Local .gem files and rake gems install

I’d like to take advantage of Rails 2.1 config.gem and rake gems
install when deploying (with Capistrano). Unfortunately, outgoing HTTP
is blocked in our production environment.

I’m considering keeping a directory of all required .gem files in our
repository and after exporting the repo on the server, pointing gem to
them with a .gemrc config file, but I haven’t been able to figure out
how to do so.

Does anyone know how to do this?

Any other ideas?