Kick start O ring

Hi
Having read the thread in 2016 that came up with the title that I am starting it appears that a SKF replacement is a better option than simply using the standard O ring.
Having completed a rebuild I did not replace it and after 300 miles it has let go big time. Strange that one minute it's fine next oil all over the place. So my question is I want to sort this properly do I replace the bush as well or are they hard wearing like the swing arm bearings?
Is there a better replacement and can I source the parts from the UK?
Many thanks

Years ago, I had my 750 gearbox bored to take a small seal insert-able from the outside. I was the same dimensions and the kick starter bush. Never had leaks since.
More recently, after purchasing my 850, I tried the x ring type O ring, with little success. I had that g/box outer casing bored to fit a hydraulic wiper seal of the same dimensions as the kick starter bush. Now no leaks at all apart from some weeping from the g/shift O ring. I run ATF in both primary transmission and g/box in the 850.

The 750 has only done about 14,000, and is still original . [ engine oil in primary and gear oil in the tranny. It is my garage queen and back up for the 850, which is my working, ride everywhere bike. Not the flashest looking but all good gear in the inside.