is there a lvl 40 Valter on some other map that I can kill for the quest

Go into Arena Assault and only have a lv 40 Valter in your team. The easy levels usually have a single lv 40 Valter with no weapon

I never thought of this. I am not clever at all.

Its best to go into arena with your lvl 40 valter, i set mines out to help others complete the challege easier as well