trolley systems are a bit of a pain!!! howver you can do it! ionics do a small 50L system but it will only keep you going for about 30 minutes!!
how about making your own, you will need a new or used electric golf trolley, then you will need to secure a tank onto it and have a 12v feed to a pump. i can make you any size tank from welded plastic and can make fixings at any points you need. i can supply a de-ionizer, 12v pump and hose reel, hoses and poles.
you will need an electric trolley as the tank when full will weigh so much. you could use an electric wheelchair chasis!!
call me on 07970 918641 if you want to talk it through!!
regards ben