You can try the following.
First, on the machine which has internet connection, run the following:
$ JULIA_DEPOT_PATH=offline_depot julia
julia> ]
pkg> add StatsBase MultivariateStats # these are just examples, add all the packages you will need here
pkg> <Ctrl-D>
Then copy the offline_depot
directory (created by Julia in the previous step) onto the machine you will use in offline mode. Then start Julia like this:
$ JULIA_DEPOT_PATH=<path-to-your>/offline_depot JULIA_PKG_OFFLINE=true julia
julia> using MultivariateStats # use the preinstalled packages here
Hope that helps.