If you want to reinforce the tubing, there are only a couple of options that come to mind. The first is tubing reinforcement using tape. Basically, along the lines of what people do with hockey sticks or even their ankles/wrists to reinforce it, take some gauze or fabric-type tape and wrap the tubing up in it, spiraling the tape along the tubing. Do note that if you choose to do this, this will definitely stiffen the tubing, thus making it less flexible. However, it will not absolutely prevent kinking; the taped tubing can still end up kinking if too much force is still applied to it. The amount of stiffening of the tubing depends on how much you overlap the gauze or tape along the tubing. Other than that, the only other thing to do would be to replace the tubing altogether with something more flexible, but that really depends on whether you really wish to take that route. Potentially good tubing which is very flexible and less prone to kinking would be good, think-wall soft rubber or latex tubing, but I'm not sure about availability or costs of such things.
Side note: regarding your first Super Soaker, it was likely a
Super Soaker XP85 Triple Shot. While the one reviewed on iSoaker.com has an opaque reservoir, there is also another variant with a clear green reservoir and black nozzle ends.
