Killing Dr Ivan, north of Alexandre in the industrial units, no longer spawns enest plans...

any ideas where?

There is no places, where he spawns, he have random chance to spawn instead of regular zombie.

ivan got a e.bandit 1 for me today. so u only have bad luck

You can get them from the trader.

From the trader, or if you really need to kill him, i'd try Martin Barracks, if hes not there he will after you kill a group or two:)