Download this and go to the hardware store and buy 2, 5/16" ID . x 5/8" OD. x 1/8" and 2, 1/4" 1" stainless steal dowel pin... I was going to buy normal barings but they wanted like $6 a piece for them. So I got angry and made this. It also rolls easier than the barings at the hardware store... Take a 1/4 drill bit and in REVERSE and drill out the holes to make them exactly the correct diameter and perfectly round. pull out 2 jack stands and find 2 C clamps and your all set.... Also I know anyone with a motorcycle and a 3D printer would know to add a drop of oil to this thing to lower as much friction as possible. So I won't....
Links to give you an example of what your looking for at the hardware store.

https://www.menards.com/main/hardware/fasteners-connectors/washers-spacers/spacers/midwest-fastener-reg-5-16-id-x-5-8-od-x-1-8-steel-spacer-5-count/74247/p-1444439958499-c-9551.htm

https://www.huyett.com/dow-250-1000