What hikers into snow country are required to do.
Google "Zip-Lok". When one gets a permit to hike into restricted areas, one of the things one gets is a "blue bag". Expected to use it for solid waste.
Actually, the last one I saw, about a week ago, was a nicer system than the "blue bag", but still a Zip-Lok solution.
(Now in weightlessness I think one would have to be VERY careful. Wouldn't want to be chasing those things around the cabin.)
Arf