For the basic stuff you are mentioning this bag may work but it also depends on the amount of supplies you want to carry. One of my ambulances has a similar bag stocked and it fits fair amount of gear with no room to spare for anything. But there are ways to save space on med supplies by using sam splints except board splints and smaller 250cc irrigation bottles instead of big 1L ones.

Look at some of the stat packs equipment. I managed to get one of the small backpacks and squized enough stuff in there to work up almost anything.

Cheaper bags like the one seen in your post when exposued to cold temperature and other elements (read trunk junk) tend to age very badly. Reflective stripes peel and crack, zippers jam and break, straps get stiff and buckles break. If you want something really cool that I saw couple of coaches use try range bag (5.11 or Maxpedition). Rectangular free standing bags with compartments for everything.

Matt