What lock can secure a 4th generation Time Capsule from theft? The 4th generation Time Capsule has a security slot at the far right of the back panel:



However, the manual does not mention what kind of lock I can attach to it.

What locks are compatible? For instance, does the Kensington MicroSaver work?
Yup, that's a Kensington slot and the product you linked will work and is on the high end in price and fit/finish. Anything compatible will work - you can open http://amazon.com and then search for "kensington type laptop lock" for dozens of vendors at various price points and key/cable configurations.