I carry a collapsible spare on a narrowed pin-drive wheel with an air cannister:
Note my extremely rare GoodYear BlueStreak SS tire
The wheel is 5" wide (the recommended width for the Space-Saver collapsible tire). This one was made by Phil Schmidt at PS Engineering - he can make a wheel to just about any width you'd like. I have also used Weldcraft in Livonia, MI (734) 420-2211 to narrow rims - they can widen or narrow your steel, aluminum, or magnesium wheel to about any width within reason. PSE will fabricate a new wheel, Weldcraft will work with your existing wheel. Weldcraft can also straighten or repair damaged steel and alloy rims.
I carry towels and bungee cords in the event I ever have to carry a flat tire in (or on) the car. So far, in thirteen years on the road, I've only had to deal with one flat, and the tire sidewalls were so stiff, that I was able to nurse the car to a service station and air the tire back up, and gently drive it back home.
regards,
Jeff