Nothing too special, just some small tweaks to the OEM shape to allow for the shoulder bolt. There's a cross-section drawing of the modifications I did, and I used the McMaster-Carr part number: 90265A133 - a 5x20mm shoulder bolt (m4 threaded). You can also purchase them through Filastruder, they are the cheapest source.
There's a right and left version so that the bolt heads appear symmetrical - you can use as you see fit.
Print via normal Voron parts settings - nothing special or even that different here.
No 6mm version because who does 6mm Z belts? Also, I stole the original model from the Voron F360 model and 9mm is what I got. Apologies to the 6mm Z Belt Crowd.
Enjoy
Jason