RonAyers does have an online OEM lookup. That's what's shows in the RonAyers link, isn't it?
As said already..replacing a kicker
without replacing the knuckle (boss...pin) is going to be a waste of your time AND your money.
There are KX kickers that fit the 'H' model KDX..an '89 KX125 'fer example.
Still, putting a 'good' kicker on a worn knuckle isn't useful.
IMO..get a new knuckle and an FRP kicker. A new knuckle does
not come with o-rings, btw. It's next to impossible to make the OEM o-rings fit, anyway. Buy some thinner rings at your local hardware store...or trim the OEM rings. That takes a sharp exacto and a steady hand.
The ring-fit comments from when I put my FRP kicker on..and that was a few years back.
'Back when' even!!
Good luck.
...wouldn't bother trying to weld that junk, either. It'll still likely bend after it's patched up. Maybe it's bent
now!.