Rocket industries resell the snow performance kits, there are other brands available here also.
50:50 is considered a flammable mix, more water than meth should technically make it an inflammable liquid under normal conditions which I would rather have as my tank sits in the boot.
I have a snow performance MAP controlled kit and their 2.5 Gallon tank, for street use that tank lasts more than 6 months, however for race use I am with R31Nismoid, I wouldn't be recommending the smaller tanks for that purpose without some sort of safeguard in place. You only get a few minutes of full throttle full boost driving before its all gone. If your ECU supports switching between ignition and fuel maps you can run two maps, one tuned without the WMI and one tuned with it, then use a fluid level switch to switch the pump off and the maps over when the fluid runs low. The same principal can be used to switch a boost control solenoid off to lower the boost if you don't have the other features.
Just because they don't sell you a fancy box to do these things doesn't mean you can't do them with the other kits and $5 worth of parts from jaycar