If this post is still up, the item is still available for sale:
Onewheel GT 6" hub cover and axle carriers = $160 for all
Both were made by Tech Rails and sold by Bob's Stoke Shop.
I replaced the motor in my 10k miles old GT with the 6" GTS motor, so I don't need this modification anymore. I have been using this with a 6" hub from my old XR it treated me well for thousands of miles, and it also solved the infamous motor overheating problem. The axle carriers center the motor in the GT after using the hub cover modification.
Cash only and pick up at safe exchange location in Fremont, CA