I just found out Thule bought out Sportworks. You want an adapter like this
http://www.rei.com/product/151060.htm? This is for a 2" hitch. If you have a 1 1/4 hitch, check and see if any dealers had the old part which is very similar. Or just get a welder to create an adapter for you. You can see from the image, the part is basically 3 square tube welded together.

I haven't heard any comments from you, so don't know if interested any more. The clearance is about the width of a full bumper, guess about 8 ".

Good luck