I don't anyone ever made outside 3rd track. If you can get more of the gargraves with the extended tie, that would be great. From the photos I have seen, guys would screw flat head brass screws into the extended tie or the benchwork, and then solder a brass HO rail to the to top of the screw. NS ho rail would work better probably.
Since it is a very old technology, it is going to be hard to find.