Should a non-disclosure agreement have a clause for non-circumvention if the US manufacturer also has outsourcing entity in China?

Since you are dealing with the U.S. entity only, the classic solution is to: (a) give the party with whom you are contracting the express right to show the design to third parties, provided that the third parties have executed and agreed to be bound by the agreement (which your counterpart needs to take care of); (b) give you indemnity against any breach by the third parties; and (c) consent to the jurisdiction of the U.S. courts for breach by your counterpart or any of the third parties. An attorney can assist you with this.