You can purchase all the parts needed to rebuild the lower steering stem bushing separately or you can buy it cheaper in a kit. I have used and will continue to use the Pivot Works kit. It is part # PWSSK-K06-400.
Here is a link to the kit needed. It will include everything you need including grease to rebuild the lower bushing
Pivot%20Works%20Steering%20Stem%20Bearing%20Kit
Here is a link to the kit needed. It will include everything you need including grease to rebuild the lower bushing
Pivot%20Works%20Steering%20Stem%20Bearing%20Kit