These people make stuff that almost identical to the westfalia stuff.
http://www.recmar.com/" onclick="window.open(this.href);return false;
track http://www.recmar.com/tracks/products_3110.htm" onclick="window.open(this.href);return false;
slides 3050 type
Hope this helps.
Track on westies is riveted to the body thought the center of the track the profile shown has the extra section on the top the the type I have seen used is only a C section you might be able to cut the extra off.