Is it permitted for me to sell online a wrist watch with a cross on the face and band of the watch?
Yes, this is fine, and there is no need for any concern.
The Rema (Yoreh De’ah 141:1), based on the Mordechai (citing from Raavya) and Terumas Hadeshen (196) writes that crosses made for jewelry do not constitute a prohibition of idolatry. The Shach (6) is more stringent, requiring that we know the cross was not “worshiped.”
In the case of a watch, there is of course no concern at all for “worshiping” the cross, and it is only there as a decoration. Therefore, it is permitted to derive benefit from the watch and sell it for its value.