Boost Factory R32 GTR / GTST Rear Wiper Rubber Delete Plug

Boost Factory R32 GTR / GTST Rear Wiper Rubber Delete Plug 

This plug is what you have been looking for. The window wiper hole is an off size and makes finding a generic off the shelf rubber grommet difficult. Generic off the shelf grommets also do not seal and generally allow water to enter, causing damage.
The other options on the market are made of aluminum and risk cracking the glass during installation.

Water tight, offers a sleek appearance and simple installation!

Boostfactory.ca  subtle engraving can been seen up close. Blends in nicely at only a short distance away. 

Sold individually.