The K’Foam Store page dedicated to the Vivaro 2002-2014 offers specific products to camperise this model, including:

Folding Mattresses: Designed for Renault Trafic, Opel Vivaro and Nissan Primastar, with viscoelastic options.
Bespoke Viscoelastic Toppers.
Mattresses for Camper Raised Roofs.
Universal Folding Mattresses in 6 pieces.
Wall Pockets with self-adhesive and Velcro.
Made to Measure Foam Covers.

These products are designed to improve the comfort and functionality of the camper