Series 1 - Framebreather F28 Packing

[sharvs]

I am running a standard set up on a S1 125 framebreather with an MA18 BS5 still breathing through the frame.
However, in opening up the F28 frying pan casing it is missing the internal mesh filter..... which in turn is having a significant effect on running (when opening the throttle). I have packed it with some K&N filter membrane which serves the purpose and is getting things moving but i'd like to get it back as it should be.
Would anyone know where i might get the original packing for the F28?