Permanent summons are best done with Epic spells. For a non-epic solution try this: -
Permanent Summon Monster
Conjuration (Summoning)
Level: Clr 9, Sor/Wiz 9
Components: V, S. F/DF
Casting Time: 1 full round
Duration: Permanent (D)
This spell is identical to Summon Monster 6 except that the...