I've looked over at the various "popular" part sites but can't find a ladder brace. Those have always been the best thing going to get a FOX convertible tightened.
They were made by Kenny Brown, who went out of business a few years back. I know they re-opened but I cant seem to find them on the web, be best to contact MM, Griggs or Steeda, the roadrace guys may have something for ya..