I carry a very compact scissors jack that I bought at a swap meet. I had a saddle fabricated for it that matches the width of my frame rails.
For a spare tire, I have a 15" Goodyear inflatible spare tire on a specially-made 5.0" wide PSE FIA wheel. Worst part is that if I ever have to use the "air bottle" I have with it, it looks like it will cost about $250 to replace it. Have to find out what the inflator bottle is charged with, and get my empties re-charged.
The collapsible fits up "tucked away" on the ledge between the battery box and the Halon bottle.
So far, I've only had one flat with my ERA, and the sidewalls of the Goodyear Gatorbacks were so stiff I was able to limp to a service station with the tire totally deflated. I pumped it back up at the service station, and limped on home with it.
regards,
Jeff