Interior storm window (magnetic)
 

I am trying to reduce noise from a road and interior storm windows seem
to be just what I am looking for (an exterior window is not mountable
on my style window). My question is how can I go about buying this? I
have found a few internet sites that sell these windows with magnetic
tape for a seal but they seem costly considering all the shipping . Can
I buy / make it locally? Or am I forced to buy it from the internet?