I guess everyone's level of commitment to the hobby varies; I know for a fact that if I had to drive an hour every time I needed water...especially in the kinds of quantities which you will need...I'd be out of the hobby.
So...have you considered every other possible source? Can you collect rainwater? It's a relatively small initial outlay of cash, and pretty much zero thereafter. Collect from a local natural source? Distillation or RO treatment for your tap water?
When you refer to "high-quality" water, what aspects of the water are you referencing? If you have clean water that is simply not chemically ideal for Oscars...and many keepers fall into that category...you could consider other species more suited to the conditions that you do have.
You are essentially describing a nightmarish scenario where acceptable water is very time-consuming and labour-intensive to provide...but you have opted to maintain a large, fast-growing fish that normally displays a prodigious appetite and is a known poop-machine...and you want to do it in a tank that is really very small for the purpose...and you want to keep other fish in there as well! You seem to be making this as difficult as you can...
