very common fault with the sr, had it happen to 2 of my sr's. piaggio dealers do them for under 20 the pair. or pm shiney red for a poly bush kit. works a treat
my mates just had an uprated set ordered for his sr that involve using 2 bull bearings each side i think Not cheap at £40 but apparentelly there the bollocks. ill see if i can get some pics. there not fitted yet so he might sell them