With some Californians fearing the spread of radiation from Japan to the Golden State, there might be a heightened demand for nuclear radiation detectors. It may be hard to find them at your local store, but there are a number of detectors available to order online, from old school Geiger Counters to key-chain -sized pocket devices.
Here are some options:
You can order Cold War-era Geiger Counters made in the '60's, from this surplus store in Pennsylvania. The big, yellow box-like device sell for $29.99 and runs for 150 hours and were made in the 60's, but the website warns that it isn't guaranteed to work.
The K8 is a $155 device that its makers call "a miniature radiation detection device ideal for all day personal carry."
A similar product, the $179.95 NukAlert, attaches to keychains so there's never the worry of losing it, unless you're prone to misplacing your keys.
For those really looking to invest, there's the NeutronRAE II Radiation Detector for $2,200. The waterproof device has more than one alarm, and detects radiation of different types and levels.