Just like everybody else, single parents are flawed. Sometimes single parents discover they are so hurt by former relationships that they have sworn off having more children, because of the damage already done to their current family. Other times single parents have raised their children to a point that they are "up and running," and they just don't want to go back to the basics of starting over again. To be honest, neither one is wrong if that is truly how you feel. If you are iron clad about your decision, then you need to find someone who is permanently okay with your decision. Notice I said "permanently okay" and not "temporarily okay." It's always a sad day when a person thought they could handle not having anymore children only to find out they would like to have a baby with their new spouse whose completely against the idea.
Don't waste people's time and don't conform to what you think they want from you in this area. In my opinion, deciding to have more children or not is a deal breaker. There are just some things in life that you have to take a stand for. If you don't want more children, then stand for that. If you do want more children, then stand for that. Just be honest with the person you are dating. You cannot be "wishy washy" about this, because the stakes are too high. Whatever you decide just know that there is someone out there for you who will respect your decision.