Wax on, wax off..
Ordinarily I don't brag about quick fixes, but this one is worth bragging about.
As anyone who uses a Sandisk Cruzer Mini knows, the cover falls off ALL THE TIME. It's very annoying. This evening I thought to myself "Well, if I put in something small to act as a shim, this should take care of the problem."
I found my shim. A folded piece of silver paper that you tear off whenever you open a pack of cigarettes. I used half of one, fit it to the small cover, then pushed the USB port to form fit it. Works like a charm. It keeps the cover tight and snug so it will never fall off. The coolest part is that it's silver like the rest of it, so you don't notice it unless you look really closely.