If I find a better way, I'll give you a hint. Until then, someone more into colors might know more about the color.:biglaugh:I've got a similar problem but haven't found a solution other than mixing my own using an in-exact but actually not too bad mix of various plastikote and vinyl greys and blacks from Halfords.
Only problem is, I have to mix it each time by eye.
If you do find a solution that is a little more 'proper' I'd love to know. Good luck.