Far as I know you can't get a new one. Not from Honda anyway they sell them as a complete assembly. My advice to you is pack it full of grease every once in a wile and it'll be fine.
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Pictures of my 300X1983 Honda CR125R - Too many mods to list
1987 Honda Powroll TRX300X Too many mods to list (District 14 #570)
KNOWSALOT Facility enginer - E6