I recently added ZunSport grilles to both my Cayenne and Taycan. The grilles are easily installed without bumper removal.
The grilles have built in brackets that hook behind the edge of the openings. You poke them in place using a screwdriver. They have a wide selection of grilles for different Porsche models.
They are located in the UK, us.zunsport.com is their website.
Here is what they look like installed on my Cayenne. For my 2015 model the outer grille openings are filled by three small grilles and the radiator opening is covered by one large grille.
Article and photos by Rob Van Name.