A 12oz cartirigdge will almost get you to about 100psi.
For me, that's plenty to get home on. If I want more, then I'd use the 16oz..
I get them for $3 each. Since I only have carry one tube, I don't need unlimited air. I want it to fit under my seat. I don't want a pump in my pocket or attached to my frame. Less is more. Heck, if my tires are stretched enough, I don't even carry levers.
And I always carry a small piece of Tyvek material in case I need to patch a hole in my tire.
And always have one good friend who will come and pick you up when you're stranded.