Title speaks for itself. I think he will have Grookey cuz he is quirky enough, though arguments can be made for Scorbunny. I think his new female friend will get Sobble.
Really any of them could. The grass and fire ones seem so outgoing like Ash, but I could totally see a scared Sobble getting spooked and hiding behind ash and ultimately becoming a confident final form pokemon, a bit of it's own arc