Buying refurbished S25 Ultra?

Where's the best place to buy a refurbished phone? I was looking at blackmarket but am now hesitant due to reviews I've seen. I have an S23 Ultra and planed on getting the S26 Ultra, but after seeing no storage upgrade decided it wasn't worth the price for me. I need a new phone. Where would y'all recommend I look for refurbished S25s?