T-shirt advertising at conventions?

If someone wanted to hire a person or a few people to wear a t-shirt of their website at a convention,how would they find people to do it? Im considering doing it for a convention later this year.

They just hire models or local ads for promotion girls.

If you do, please make sure your graphics/design are professional and person who is wearing it is at least 'decent'. I have actually seen a few of companies doing this in marketing conference but their print was just so bad that it makes their company looks bad. Not to mention that their 'model' (more like a rep), isn't too attractive neither (my opinion). It's a total fail from my perspective.

While others I met who were dressed professionally (shirt, dress pants etc.), seem much more professional to me.