I am creating a process that encompasses the influences per different resin type, and providing each of the flows with a provider. I have noticed, that in the case of e.g. PET and low-density polyethylene, the providers are available, but in the instance of high-density polyethylene, there exists a flow in the database, but there is no provider provided. Is there any other option to add a flow for HD-PE? I am using the ecoinvent database, and all the other flows are from the category 2013: Manufacture of plastics and synthetic rubber etc.