I picked up this Souvenir “Mamesara” plate on Ebay.com. It’s from the 2015 Tokyo Star Wars Visions exhibition. It wasn’t cheap, but i figured that as a collectible souvenir it wouldn’t really be readily available in the future.
The plate itself measures 8.5 cms in diametre and comes with a certificate of authenticity and a nice little box. There’s one more available here.