Have you just upgraded your Shapeoko 3 with their older Belt-Z carriage to a brand new Z-Plus carriage?  

Here's a list of parts you'll need to continue to use your z-independent dust boot:

Required:

• Z-Plus Plastics:  https://pwncnc.com/products/bracketing-plastics?variant=39677022929035
• Z-Plus Screws:  https://pwncnc.com/products/bracketing-screws?variant=39677023518859

If you're upgrading from the "J" shaped track brackets, then you'll also need these aluminum straight tracks.  But if your belt-z bracketing already has these aluminum straight tracks, no need to purchase them again.

• Aluminum Track Brackets:  https://pwncnc.com/products/bracketing-tracks

Optional:  (assuming you still have them from your current Belt-Z bracketing system, then there's no need to buy these again)

• Standard (B) Support Arms. The are shared among all of the Shapeoko 3 Z-Independent Brackets: https://pwncnc.com/products/support-arms?variant=39677034102923
• Thumb Screws:  https://pwncnc.com/products/bracketing-thumb-screws