Depends how much of a complete solution you want. You could try fabric dye (as the headliner is fabric).
If you intend on re-trimming it, with suede or such alike, then i would recommend spraying some resin over the fabric first, to give you a more rigid base to apply your material to. The glue you use may struggle to stick to the fabric and the longevity of the retrim may suffer.
Failing that, buy a Leon Cupra R black headliner from eBay or a breakers yard!