I make this attachment for the Spyderloks but it could attach to anything with a couple of bolts thru the crossbar. May be a little overkill for what you want but it offers alot.
Name:  Spyderlok2.jpg
Views: 1011
Size:  81.4 KB
Name:  Spyderlok1.jpg
Views: 999
Size:  100.9 KB