Yes, I have seen certain types of holders at Walmart. They are sold in the automotive department as cellphone holders. Radio Shack also sells cellphone holders, some types of which will also hold scanners of course; just go online to Radioshack.com and do a search.
It all depends on where you want to mount the scanner. On the dash, on the center console, on the door. There are holders out there that will mount in all these locations, you need to deceide where you want to mount it. Also try stores that sell cell phones and accessories, they usually sell car holders that will work with scanners.