We also have a new Sunseeker; and after an exhaustive search, we ordered one-piece custom cab floor mats from Lloyds Mats and just love them. Just arrived this week after ordering them 8 days ago. Perfect fit! Just search for Lloyds Mats, enter Chevy Express 3500 (or whatever your chassis model is) and walaa, it's custom made! They cost around $180, I believe. Here is what they look like:
Excellent quality and very plush, they fit around all the humps and bumps and curves perfectly. Just what we wanted.