SM-G99xU is the model number you want for US carriers and it has the Snapdragon 888.

This is the listing: https://www.amazon.com/Samsung-Factory-Unlocked-Smartphone-Pro-Grade/dp/B08N2FRMPN/ref=mp_s_a_1_3?dchild=1&keywords=galaxy%2Bs21&qid=1611356520&sr=8-3&th=1&psc=1