I got this from Honda Automotive Parts website. The part number is the first number. It is based on the color of the van. It doesn't appear you can buy just the cover. These are the 2008 part numbers. If you go to the www.hondaautomotiveparts.com and search for your van and then look at the Radio Antenna category and you'll see it. For the 2008 it is Item 2 in the graphic.
39150-shj-a11zb antenna assy., xm *b530m* ocean mist metallic
39150-shj-a11zc antenna assy., xm *b92p* nighthawk black pearl
39150-shj-a11zd antenna assy., xm *nh578* taffeta white
39150-shj-a11ze antenna assy., xm *nh678m* silver pearl metallic
39150-shj-a11zf antenna assy., xm *nh679m* slate green metallic
39150-shj-a11zg antenna assy., xm *nh705m* nimbus gray metallic
39150-shj-a11zh antenna assy., xm *r529p* dark cherry pearl
39150-shj-a11zk antenna assy., xm *b547p* baltic blue pearl
39150-shj-a11zl antenna assy., xm *yr573m* mocha metallic
39150-shj-a11zb antenna assy., xm *b530m* ocean mist metallic
39150-shj-a11zc antenna assy., xm *b92p* nighthawk black pearl
39150-shj-a11zd antenna assy., xm *nh578* taffeta white
39150-shj-a11ze antenna assy., xm *nh678m* silver pearl metallic
39150-shj-a11zf antenna assy., xm *nh679m* slate green metallic
39150-shj-a11zg antenna assy., xm *nh705m* nimbus gray metallic
39150-shj-a11zh antenna assy., xm *r529p* dark cherry pearl
39150-shj-a11zk antenna assy., xm *b547p* baltic blue pearl
39150-shj-a11zl antenna assy., xm *yr573m* mocha metallic
