I appreciate all the replies. After careful study and research, a RO system is not practical. Other under counter systems don't do enough, leak, can't work with an RV water pump or have other issues I find unacceptable. So, it's bottled water for us when we RV and don't fill the Fresh Water tank except when we know and are sure of the water source, such as at home. Most public fills are not safe 100% of the time as there is just no way to know what the last guy did to the hose bib prior to me using it. I don't want to risk contaminating my fresh water tank.
I realize I'm a bit paranoid on this, but believe me, a case of giardiasis is nothing to sneeze at. We had it once from a local restaurant and it put my wife in the hospital due to dehydration. The health department came out to our house and tested everything; swab samples from the counters to the eggs in the fridge. I kept telling them it was the restaurant and eventually that was their conclusion. Took a month to get back on my feet and 6 months before I was 'normal' again.
Maybe I'll just stick to drinking beer.