What darkstorme said.
The only option is to use the Censer of Arcane Devotion, found in temple stores, which aligns an arcane caster's summons with that of his/her deity. However, if your character does not follow a deity, it does not do anything, and it reverts to alignment-based summons. The Censer is not intended as a way around anything. Rather, it is a focusing of one's devotion, affecting what creatures a faithful individual summons.
The possible conflict you described there is just one of the challenges in playing evil-aligned characters.