Gigalith Crest: gives a Solar Power buff (increased SPA in sun), but maybe more powerful and certainly without hp cost (and maybe activate it in some fields as well)
Reasoning: the Pokedex says Gigalith can fire powerful energy blasts when the sun is out, and it can learn such moves (like Solar Beam), but its SPA is too low to use them
Edit: or just swap attack and special attack, that can work too