I carry a plug kit in my 911 and it is so small it just stays in the trunk. I have never needed it, but I also carry a can of fix a flat that is old enough I may toss it and get a new can. In the 911 as all you likely know it is a royal pain to get a flat in the rear. Jack up the car, remove both front and rear tire, put the front in the rear position, put the collapsible spare tire on the front, and find some place to put the dirty flat rear tire. On a road trip with my wife the car is packed full and I honestly have no idea how I could do that.
I have been lucky in my 25 years, and 41 states of roads trips and I have not had one flat.
This all came out of my 911 and I left the tool bag and car washing bag in the car.