51414_NF5_611 BUSH. guide
51414_NX5_701 BUSH. guide

Have a look here: http://tsrworldwide.com/

Click on the parts list on the left had side of the page and select RS250 then scroll down until you see F5 front fork. This will give you a break down of all the fork components. I could be wrong (hopefully!), but I think one or both of those bushes are discontinued.