Several years ago I sowed M. hahniana from seed obtained from the DeHerdt brothers in Belgium. This is the very hairy type. I do not know if DeHerdt still sells seeds. I think that it is very unlikely that they will have a website.
Mesa Garden (Belen, New Mexico, USA) does list M. hahnian and adds 'long white hairs'.
Wolter ten Hoeve, The Netherlands.