I found MSR chlorine tabs and a Sawyer microfilter in Wally world, which brought them into my price range. Plenty of water here in SE Florida, but the range of bacterial contaminants is terrifying. That prompted a review of my information on using sodium hypochlorite/clorox for water purification, and renewed a longstanding irritation about the cavalier use of "drops" as a unit of volume. Drops ain't uniform: iv administration sets can deliver 60 drops per milliliter or 15 drops per milliliter. Depends on the diameter of the drop orifice, viscosity of the liquid, and probably some other stuff of which I am ignorant. I did find a CDC reference that offers both drop notation and metric equivalence: 8 drops/ 0.75 ml per quart for clear water, 16 drops/ 1.5cc for cloudy.

This gratifies the physical chemist deep inside, tho the organic chemist aspect of my personality suggests that drop measurement is close enough.

Edit: Consensus also seems to be that regular vs concentrated clorox are not different enough to warrant a change in volume used. Metric syringes are widely available through pharmacies, craft stores, and American Science and Surplus website (sciplus.com, no affiliation).