So this is good, actionable information; thanks!
I looked, did not find (point it out if I missed it?) information/links to the "water purification tablets" that you mention. This prompted me to find and share this:
Not sure if it's suitable for field application, but I think it probably is? I should do some more research. It came to mind because I've been personally investigating MMS/CDS for a while now, finding it remarkably beneficial, and had heard of its reputation as a water purifier...
Oh, and I almost forgot...
!PIZZA
There are a lot of brands and options when it comes to the tablets. They're in just about every camping goods section of every big box store under the Coghlan's brand, Katadyn has a name brand version, and there are a bunch of options at sporting goods stores. I don't know anything about the drops, but that doesn't mean much. My knowledge is limited.