We had these 316-grade stainless steel pins specially made to fit the KC-02 piston as DIN and ISO standard pins don't have suitable end shapes to seal in the piston.
Lots of people lose these tiny pins, they are included with our V2 pistons now, but these spares are also available here!
Price is for 1 piece in a wee little baggy, all on its own :,,,(
(Please don't order just this tiny pin on its own and have me ship it to the other side of the world, that's really annoying)