I am not claiming this is the "best" jack; however it did meet most of my criteria for a portable jack that I can use on the road to make a tire change. I am using a military Humvee jack.
The pros: The jack has a very wide base (good for stability), is rated at 3 1/2 tons (well over the entire weight of the car), has a pivoting contact point (keeps full contact with the car as the car is raised), easy to set up, comes in its own carrying case and is of moderate weight (23 lbs.)
The cons: Minimum height of the jack is 6 3/4" (with adapter). With my suspension set on high the jack fits under the car fine. However with a flat tire, I am pretty sure a small ramp will be needed to rest the flat tire on to allow enough clearance. Price and availability may also be an issue; one needs to use the internet to find these at a reasonable price or be near a military surplus store. I would only buy "new" to insure a jack that has not been abused. The price ranges from $50 to $200. Here is a link that has them at the lower price end:
U s G I Scissor Jack Heavy Duty Car or Truck Jack | eBay
Some folks will not use a scissor style jack, citing safety concerns. i get that, however this jack has a wide base and is rated at 31/2 tons and it's contact point pivots to maintain full contact with the car's jack point. These attributes hopefully addresses those concerns.
The jack has a 7/8" diameter tip that is the lift point of the jack. Not owning a Humvee, I imagine that this tip fit into a mating hole to provide a secure lifting point. However, the jack's tip is to large in diameter to fit into the MS jack point hole. I didn't feel comfortable having just a 7/8" diameter contact area and made an adapter that fits over the 7/8" tip and provides more contact surface area between the jack and the car's jack point. The adapter consists of a 3" hockey puck sandwiched between two 3" aluminum disks. The hockey puck and one of the aluminum disks will need to have a 7/8"-1" hole center drilled into them. One could try the hockey puck by itself; I wanted more support than just rubber so I choose to use the aluminum disk as well. A source for the 3" aluminum disks:
Aluminum Round Disc Circle 3 Thick | eBay
I also carry a 24" breaker bar and 21mm 6 point deep socket; my ramp is made of scrap 2x6's. My plan is to raise the suspension to high, drive onto the ramp with the flat tire, place the car in jack mode and then place the jack with it's adapter under the car and mate the adapter to the car's jack point. It worked on the dry run, hopefully that's the last time I have to use it.
Here's the photos:
