It is a shame that a kit resource has been lost.
As time consuming as it is, apparently the only solution now is to scratch build Goldberg kits. Fortunately I have plans amassed over the years that make it possible, and that Goldberg kit plans contained enough detail that one could scratch build. One kit that comes to mind is the Jr. Skylark. It's back burner for now but some time future would scratch build as electric. It's twin motor mounts lends itself to small outrunner motors, without the hassle of attempting quick starting of two Cox Tee Dee or Pee Wee .020's and a longer run time than their small tanks allowed.