I know what your trying to do!!! Haha. I have the circular stone and the human sacrifice.
For the urns your best bet is to buy a holographic engineer with one the urns. Take than urn and find a way to mold it. You could then make several of them. I think you could possibly use clay for the mold.
For the circular stone and human sacrifice try eBay, Amazon, toywiz, bigbadtoys, cmd store, and lastly Craig's list. (I actually think I saw one of these two items on Craig's list a few months back.
I'm guessing you le looking for six corpses, one stone plate and a few pillars to create a diorama. I understand I do model making and was planning on undergoing a similar project.
P.S. Since you are interested in creating a sort of engineer or avp diorama head of to Martinocatalano website. He sells an engineer ample chamber head that is to scale with the Prometheus line.