My understanding is that hosts that have been spit out by a communicant who is unable to swallow must be dissolved in water and then the water is poured down a sacrarium. But what do you do if you are visiting a nursing home or a homebound communicant where it is impractical to get to the sacristy? The GIRM is vague on these special circumstances.
The only practical thing to do is to pick up the host with a handkerchief or paper towel and bring it to the sacristy. It may be inconvenient, but this is the body of the Lord. Nothing deserves greater care and consideration.