I bought a small Dynaplug kit off Amazon
, and keep it in the boot. I figure it will handle anything I'm likely to encounter.
That said, we also have AAA, and if I did any serious road-tripping that would be my backup. I never considered the fix-a-flat/slime to be a serious option bc tire guys hate it so much.
At one point I thought about the Porsche folding spare, but it just didn't make sense for my driving use case. In fact, in the last 20 years, I think I've used a spare tire exactly once, and that was on my wife's big SUV.