I got one. I know you need five. I will make you a deal. Its kinda reverse in your favor. I will sell mine right now for 5 billion. However if others sell you theirs, my price drops even though ordinarily the price should go up, but I am trying to give you more incentive. Here is how it goes:
Example
Promathia owns 15 rings, mine costs 5 billion
Promathia owns 16 rings, mine costs 4 billion
Promathia owns 17 rings, mine costs 3 billion
Promathia owns 18 rings, mine costs 2 billion
Promathia owns 19 rings, mine costs 1 billion
Good luck to you, and best of luck in all you endeavor.