I really can't have too many more chicks/chickens at this moment so would just one or two more chicks be okay?It would ideally be better for your lone chick to have other chicks of the same age to socialise with - particularly once momma has weaned it.
Whether momma will accept additional chicks is another matter. No harm in trying, as long as you have a brooder set up, in case things don't go as planned.
Thank you for your help!If you are hoping that momma will adopt the chicks, then yes (or the same size, at least). I've no experience in trying this, but from what I have read, adoption has better chances when the chicks are no more than a few days old.
I hope that other members with direct experience will be able to advise further as this will be of greater benefit to you.