I'm not willing to drop $600 for a Swarovski crystal DS Lite cover, but I am willing to throw down $14 for the Dragon NDS Lite FM Radio Converter. The converter features a LCD display and stereo sound signal with full range of FM radio frequency, new compact design. It plugs straight into your DS so you don't need any additional batteries or power.
The adapter is available from Hong Kong importer DP Mega, but the company sells their gear on eBay so it's pretty easy to get a hold of and you don't need to worry about translating the website. I rather like the idea of rocking out to my favorite morning radio show with my DS Lite.