I've cooked up some bitter almonds. These contain small amounts of cyanide (similar to real bitter almonds) and so are meant to be fed to toxic norns. While the cyanide has no beneficial effects on the toxics, it does not seem to have a harmful effect either, at least not in my (admittedly limited) testing.
These have been tested on other norns as well, and a single almond is enough to kill a non-toxic norn, so be very careful when introducing these to your worlds.
If you find any bugs or other errors, please let me know.