Yeah, they're a good thing to have. Here's an article that might give you some ideas. However, it's a few years old so I'm sure there are newer, better radios out there now. I suggest just doing a web search as there are many websites that focus on safety gear. Some portable NOAA radios are also FRS radios or CB radios or AM/FM radios...or a combination of several of these. Some are crank-operated so you don't need batteries. Some also have flashlights or sirens. There are numerous options so you would just need to pick the one that is right for you. The cheaper options seem to be about $30 or so, and the prices (and features) go up from there.
You might want to look for something with SAME technology. This is a bit of a mixed blessing for the roadtripper, especially if you're going to be going over multiple states. SAME means that you plug into it codes for the areas your driving through. So, if you're traveling a lot, you will need to do this fairly often and will need to print out the list of codes to have with you. The advantage is that you will only receive warnings for the area you're in. You don't want to be in Nebraska and get warnings for Kansas. Especially when you're traveling as you may not realize the warning doesn't apply to you when you're not familiar with the names of towns, etc.