Thanks for the ideas. When I get one, it will be a small, evaporative, one that turns off when it reaches a certain humidity and turns on when it falls below it. That limits the purchase to just a few of the many humidifiers that are out there. I'll probably go with the Vornado Evap2 (4.4 stars at Amazon) which gets mixed reviews, but overall a nice score.
The fish tank caught my attention, but would have to create a sliding top that opened and closed automatically at certain humidity so we could get away in the winter more than a day or two. They have automatic feeders and water level controllers for tanks, why not an automatic fish tank humidifier complete with humidistat and sliding top. Or as Steven Wright might say, leave the fish tank open on top, get a dehumidifier for the room and let them fight it out.