Firstly I would suggest that you chase the manufacturers up for an EPD. If they claim to be sustainable, they should back that up with an EPD. As consumers, we need to make it industry standard practice and hold manufacturers accountable for their claims to reduce green-washing.
If there is no EPD available, the next step is to find out from the supplier/manufacturer what exactly that product is made from and then find a material that is most suited for this product. From their website, it looks like most of it (95%) is made from recycled PET. Unfortunately, it looks like we do not have PET in our material library. I believe the “Insulation | Rigid Foams and Boards | Polyethylene | Polyethylene” material would be most similar to your product. The conservative approach in lieu of an EPD, would be to go with this material as a proxy. However, please pay attention to the weight/density of the material when you add it to your design/template. I would recommend adding it by weight rather than volume.
Hope that answers your question!