Ive just spent the last 30 mins llooking around for a template of one, lousy search is down, ive seen it here before, but i cant find it,, any help please?

I'm not gonna bother looking for the post on the template, but I'll tell you how to make your own.
I've only tried on Photoshop so I dunno if any other programs have all the features or not.
Start a new file, around 500x500 pixels.
Fill the background with black.
Take the circular elipse tool, make a perfect circle (hold down the shift key) then right click it and "Select Inverse." Then delete.
Put what you want there, I used a Master Cheif picture I'd found. If you want it to stick out, put a glow behind it.
Go to File>Print With Preview and change the size from 100% to 1.6x1.6 inches. Position it wherever you like, then print it. But if you want a really good glow effect only behind certain portions make sure you use photo paper.
Cut out the circle as close as you can, and put it in the controller.

If you figure out a simple way to have the jewel stay on, let me know.

Hope you find that useful!

I haven't seen a template for the Duke, but I have one for the controller S.

PM if this is what you need.