Hi,
there`s a bloke from the US, Zach Allen, who makes spanners for the Korean airguns. Reason he makess the spanners is to avoid this:
Here`s Zach`s mail adres: sonargodz@hotmail.com
Spanners cost $18, mail the make and type of the gun you have.
Zach tells me in his mail Viton o-ring sets are on the way too!
Cheers, Fokke Mol