I've used these guys with great success
https://www.paints4u.com/ProductDeta...productID=5021
You can send them a sample (which is what I did) and they will replicate it, including the degree of matt-ness of the sample. I sent them a sample of Tektronix blue, and what came back was superb.
If you don't have a sample, they can probably base it on a RAL colour too.
Craig