You can buy wheels and feet separately for the 2019 Mac Pro, but they are quite expensive (via 9to5Mac) like the Mac Pro itself.
The $699 Mac Pro Wheels Kit offers you four stainless steel wheels which you can mount, if you’ve equipped your Mac Pro with the regular feet and want to give it more versatility. But you should be mindful that when you purchase them as part of a Mac Pro setup, they come out cheaper— they cost $400 when you purchase them as part of your initial setup.
The $299 Mac Pro Feet Package lets you mount four stainless steel feet on your Mac Pro. If you set up a Mac Pro with wheels before you bought it, you should mount the feet and make sure your Mac Pro isn’t rolling around.
Both kits are now eligible to order.