It might be helpful to think about seeking consumer perspectives rather than consumer representatives. If you want a range of perspectives, involve a range of consumers, and give the consumers you do involve the time and resources to network with other consumers. It's important to think about your reasons for involving consumers when answering this question. If you want two consumers to sit on a research steering group, they will need to willing and able to participate in meetings, supported by a consumer organisation, and able to put their views across to a variety of people. These people may not be 'typical', but they will be able to contribute important insights from the consumer perspective and will be also able to access and present a range of consumer views.
Research shows that consumers and professionals often have different priorities for research.
Even when health professionals are patients they may have a dual agenda. For example, in Australia the National Breast Cancer Centre carried out a study to discover the views on priorities for research in breast cancer as seen by various stakeholders, both researchers and 'consumers of research'. They found that women with experience of breast cancer saw priorities differently from researchers. They made 'risk factors' their highest priority for research, a topic that came fairly low on the scale for clinicians, researchers and policy makers.