Hi Steve,
If you did the scrape and scope on the dead fish, then you probably would not have found anything. Parasites quickly evacuate for a new host. This needs done on a live fish. No to the RO water...
How many fish are you going to be dealing with? A stock tank is very portable and quickly set up, get one from a feed store, for a hospitol tank and your going to need filtration and 02....
You can get slides and slip covers from Pond RX or if you have a store like the Learning Tree around, Someplace that sells scopes should have them...
I'm sorry your loosing fish Steve, and yes, your going through a stressful situation.

Believe me, we've all had heartbreak and hair pulling bouts. We call it the book of learning.... But your not alone!