Weatherboarding / Featherboarding

I'm trying to get weatherboarding to match what is on a house extension that was added 20 years ago. The weatherboarding as installed at the thickest end is 16mm thick x 140mm wide x 5mm at the thinnest end.

I've tried three national timber merchants and all they stock is a sawn so-called ex 22mm x150mm x 5mm but the thickest end at the three firms is only 10mm.

I want it to match the existing. Is it still possible to get weatherboarding of 16mm thick?

I would be happy to get either 140mm wide or 150mm wide.

You could go to a saw mill and have them cut to suit. Probably end up with better quality anyway.

Saw mill is good advice. Rang one and they can do any size.
Thanks freddiemercurystwin.