I can't find anything about the active ingredient in Derris Dust being outlawed, so it still should be available. Pyrethrin will kill many of the same insects, but is less easily available in powder form. If caterpillars are the main problem, you can use Dipel dust--assuming it's available where you are--which is a bacterium that only kills caterpillars. From there you get into the synthetic pyrethroids--such as permethrin or resmethrin--but, while these are relatively non-toxic, they still are not considered organic.

derris dust contains copper which will be banned

Actual Derris dust is made of rotenone, though it is often combined with copper-based fungicides to make a dual purpose treatment. Rotenone has recently been implicated in the development of Parkinson's disease.