Cushion covering fabric source and also can they be dyed?

[Jodel]

Hi,
I have just bought a Kelt 29.  It has the light grey/white checkerboard pattern fabric on the cushions.  The corner cushions are missing and I need to make up new ones to match the existing. I know it is a long shot, but where might I find matching fabric ? I am also wondering if the existing fabric can be dyed?
Jodel