Minor schemas (Magic of Eberron, p122) can be made for spells up to 6th level, and you can use the spell in it once per day. The energy immunity spell (Spell Compendium, p80) gives the target immunity to the selected energy type for 24 hours. If you make 5 minor schemas of energy immunity, you can use them on yourself at the start of each day to gain immunity to acid, cold, electricity, fire, and sonic damage. The total market price for those is 132,000 gp.
Combining this with previous ideas, you'll need fewer minor schemas. If you play a lesser mechanitrix (Fiend Folio, p137 and Player’s Guide to Faerun, p191), you get electricity healing.