Hi, thought someone here maybe interested in this. It's a 3D printable stand I designed for a remote controlled BB-8.
https://www.thingiverse.com/thing:5849943
At the scale it is now, the pocket will fit a buckle that is 1.5 inches tall and up to 4 inches wide. If it were me I would go with a flat plate style buckle, picture below. Then I would Velcro the printed buckle on, making for easy removal.
After looking at your photos, the extra piece appears to be the clip for a shoulder bandolier. I modeled two different versions for a total of three. the buckle by itself, the buckle with a static bandolier clip, and the buckle with a bandolier clip that can be made to swivel. for the swivel...
I Just modeled it, and put it up on Thingiverse.
It is non functional, it is meant to be attached over an existing belt buckle. It is 4 inches wide, but of course can be scaled up or down.
Let me know if you need it to be modified. Hope it helps!
https://www.thingiverse.com/thing:5841303
I am not familiar with the character, my research showed me two different styles of buckle. do you have a reference photo of the one you are looking for?