Depends on what you're looking for. Sun teams tend to use Torkoal for SR, so if you want a Defogger, I would advise trying Corviknight to cover a lot of crucial resistances, give you a Steel type, and still check Grounds like Landorus-T. Mandibuzz is also a good replacement if you are worried about Dragapult, Aegislash, and long-term Grasses. Landorus-T is still an option, but it is by no means a staple on this archetype of team.
If you mean more in general rather than on Sun in particular, Garchomp and Hippowdon are alternative SR Grounds and the same pool of Defoggers plus Zapdos and Tornadus-T can also suffice on that end.