You can by the centre bearing seperate online but will be a massive fail, you have to cut the shaft to replace it, next to no one here will do it for you and warrant it. ive bought a couple form the states, they send you one all ready to be bolted up, and add a core charge till you send the old one back, to be fair there isnt any point sending yours back as it costs more than the core.
If you need details on how to obtain one let me know
cheers
Jmac