Not to forget The StainShield! (and a TIP!)
Add the Rubbermaid "StainShield" containers to your list! I keep about a dozen different soap cakes in these, stacked. They are thick, very clear, unbreakeable plastic, with tight lids. They travel well, too.
You guys go to colleges/schools? Most schools these days offer a shaving mug logo'd with the schools' crest on it.
TIP:
Many "artsy" boutiques which carry pottery from local artisans will have mugs/bowls that are unique, as well! I oftern carry around two cardboard disks I cut out - one for the smaller size cakes (2 1/2" diameter), and one for the larger cakes (3" diameter). When I find an interesting bowl/mug/container, I check it against the discs for sizing!