Spells to transform into a demon or devil?

[Player Killer]

My nephew is playing an alchemist and wants to be able to take on the form of a demon or devil? Are there any spells similar to Fey Form or Form of the Dragon but based on granting a demon or devil form? I'm the GM and I'm fine with third party spells, archetypes, etc. I couldn't find anything like this on the d20pfsrd. Any advice would be appreciated. Thank you!

[Lelomenia]

I think not, though it would be easy to homebrew at least a version of the angelic aspects. Demoniac gets to transform into devils as well, which could be usable or provide guidance for you. I don’t know 3rd party very well.

[Firebug]

Ja Noi Aspect is close, with Ja Noi being an evil outsider that looks vaguely demon like (fiery-skinned humanoid possesses black eyes beneath the bony ridges of its brow). Geniekind for the same reasons, picking Efreeti gets you cosmetic horns and red skin.