Advanced Race Guide has a race builder that includes half-elementals and full elementals:
VMC Druid lets you turn into a small elemental of your choice.
Magic Jar
Polymorph any object
Ummm.
Cant really think of others
Just ask the GM to make it official at level 20, you have all the mechanical advantages, burrow, immunity to crit and sneak attack from the bloodline.
If you can spare the feats, you could take the Skill Focus (Disguise), Eldritch Heritage (Shapechanger), and Improved Eldritch Heritage (Shapechanger/Mutable Flesh) feats. With those three feats, once per day you can cast a transmutation spell of your choice (for example, Elemental Body IV) and have it last for up to 18 hours at 20th level.
If you can spare the feats, you could take the Skill Focus (Disguise), Eldritch Heritage (Shapechanger), and Improved Eldritch Heritage (Shapechanger/Mutable Flesh) feats. With those three feats, once per day you can cast a transmutation spell of your choice (for example, Elemental Body IV) and have it last for up to 18 hours at 20th level.
? I do not follow. I assume that you are referring to a Shapechanger Bloodline but I was not able to find that Bloodline on either the Sorcerer or the Bloodrager that had that name, and doing a manual search for that name or for abilities with those names also did not reveal which one it was.
Is that particular bloodline 3rd party? Or is it simply not on the SRD?Also that surprises me that there would be a Bloodline that allows you to alter the duration of any Transmutation spell to hours per level. That seems obscenely powerful >:)
Elemental Savant prestige class from 3.5 Complete Arcane.
The Shapechanger bloodline is from the Legacy of the First World Player Companion. Details of that bloodline can be found here.
It takes several levels to get to the hours per level point for Transmutation spells, but it is insanely powerful once you get there.
But to answer your question. The short answer is you cant :(
Long answer is that you can do different things that would get you close, and if you are ok with you and your GM bending things a little then you can pull off a psudo-elemental, or something similar.
Easiest answer is for your GM at some point to simply give you the Element Infused Template and be done with it. It should give you most of what you are looking for, and it gives you the Earth subtype!
The Metal Clad Template might be an interesting way to about it.
Or the Chthonic Creature Template to gain the Earth subtype that way.
Another Idea is to simply be a (unarchetyped) Druid and Wildshape into an Earth Elemental, and stay in that form all the time. You mentioned being a sorcerer, so this might not be desirable. Also, there are no desirable archetypes that grant elemental forms, so you might as well stay unarchetyped.
Multiclass Archtypes (I think thats what its called) into a Druid might get you what you were looking for, but I can't find its link.
Alchemists gain access to the Eternal Potion discovery at 16th level. This allows them to turn 1 potion into an unlimited duration.
Potions, however can only be made of 3rd level or lower spells. The Fire Bomber goblin archetype changes the Elemental Body extract to be a third level extract, meaning a Fire Bomber can turn into a permenant fire elemental at 16th level.
Maybe ask for a custom Earth Bomber archetype based on that?
Another option is Mythic. Mythic Brew Potion allows you to craft a potion of any level (which you then turn eternal). Maybe have a one-off quest to get the Mythic Potion?
Again, no sorcerer :/
Next idea is Psionics. The Psion (Egoist) gains access to the Metamorphosis line of spells, which could be used to emulate an Earth Elemental.
Later on take the Metamorph prestige class, which, among other things grants you the ability to gain the Elemental Subtype and make the power permanent. He can get all this by about 15th level as well.
Again, no sorcerer :/
My final idea is to simply use Polymorph any Object to transform into an Earth Elemental. Just work with your GM to make sure the duration is permanent and you should be good to go.
Note, however that this only gives you Elemental Body III, so you do not gain any of the types/subtypes or other benefits.
Bonus is that this can be done by a sorcerer!!
At 10th level, a beast bonded witch gets Twin Soul, a magic jar like effect. With it, you can replace your body with another, such as an elemental. Finding an elemental that is not dismissable, is a bit harder. Improved Familiar is one way, but sharing your familiar's body is a bit risky in itself.
/cevah
Just say you identify as an an earth elemental.