I tried this approach, of using Duplicate form the WB, but it doesn't seem to work.
Yeah, the Kickstart disk has a non-standard bootblock, since it's not QUITE a standard AmigaDOS disk, right?
I seem to remember there being some simple trick to copying the kickstart disk, but I just can't quite remember what it is.
I think just using any standard nibble copy should work fine. XCopyPro, Dcopy31, or any number of others on Aminet (as linked by the previous poster) should work fine.