Wizards did post a psionic theurge PrC a while ago. Part of the Mind's Eye series. I have the .pdf collection they released it in, but it's too big to attach.
So here:
Ten levels, poor BAB, poor Fort & Ref, good Will
Hit Die: d4.
Requirements
To qualify to become a psychic theurge, a character must fulfill all the following criteria.
Skills: Knowledge (psionics) 6 ranks, Knowledge (religion) 6 ranks.
Spells: Able to cast 2nd-level divine spells.
Psionics: Able to manifest 2nd-level powers.
Class Skills
The psychic theurge's class skills (and the key ability for each skill) are Concentration (Con), Craft (Int), Decipher Script (Int), Knowledge (psionics) (Int), Knowledge (religion) (Int), Knowledge (the planes) (Int), Profession (Wis), Psicraft (Int), and Spellcraft (Int).
Skill Points at Each Level: 2 + Int modifier.
Class Features
All the following are class features of the psychic theurge prestige class.
- Weapon and Armor Proficiency: Psychic theurges gain no proficiency with any weapon or armor.
- Spells per Day/Powers Known: When a new psychic theurge level is attained, the character gains new spells per day as if he had also attained a level in any one divine spellcasting class he belonged to before he added the prestige class. He gains additional power points per day and access to new powers as if he had also gained a level in any one manifesting class he belonged to previously. He does not, however, gain any other benefit a Psychic Theurge (Prestige Class) character of either class would have gained (bonus metamagic, metapsionic, or item creation feats, psicrystal special abilities, and so on). This essentially means that he adds the level of psychic theurge to the level of whatever other divine spellcasting class and manifesting class the character has, then determines spells per day, caster level, power points per day, powers known, and manifester level accordingly.
If a character had more than one divine spellcasting class or more than one manifesting class before he became a psychic theurge, he must decide to which class he adds each level of psychic theurge for purpose of determining spells per day, caster level, power points per day, powers known, and manifester level.
Yes, very bland. I also found a psion/divine multiclass PrC called the monastic servant of Auppenser over on Candlekeep.com in the Ed Greenwood files, if you're a Forgotten Realms fan. Advances divine casting & spell slots every level, but only psionic manifester level every level (no new powers known).
(First time I've posted on the new boards. Wow are they slow. Or my computer is really old.

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