Here is the page from the Scottish Register of Tartans
http://www.tartanregister.gov.uk/qRe...rchString=gray

Your kiltmaker should be able to get the tartan from one of the major mills. As a point of interest I had a kilt length of 16 oz wool woven in the Royal Naval Association tartan by DC Daglish it was handled by my kiltmaker who then sewed it up into a lovely 8 yard kilt.