Not sure what do you mean by a "Centurion accuracy set", but if you do mean the bracket set, you can find it here:
* The bracket system is not mandatory, you can make your own strapping system and just retain the flat head screws on the outside.
There are also many other mod sets can be found here:
https://www.whitearmor.net/forum/forum/16-ongoing-sales-project-orders/
Also check out Joseph's guide on building your OT Stromtrooper on how to match up to the screen used sets.