Looking for office desks that can be 'closed' and locked?

Quick background info: We are going to be doing some MAJOR renovation, expansion, and remodeling at work. What this means for the employees is that most of our desks are going to have to be moved for the next several months. Some are likely to be moved into public areas. It's a library, so people wandering and browsing is common. Obviously then, we need to secure the materials on and in the desks.

What I'm looking for is a commercial size regular office desk that has a cover and can be locked when not in use. The roll top desks that I've found are small writing desks, more like you would find in someone's home, not big enough to work from.

Of course, there are desks with drawers and cabinets that lock individually. But I'm looking for something that has a cover for the desktop itself as well.

Has anyone ever come across something like this? The Google hasn't been much help in finding anything, but then I may simply not be searching the right terms.

Preferably NOT something custom made (ie. crazy expensive).

Any hints or suggestions would be greatly appreciated.