Mahonia Aquiflorium

I wonder if anyone could assist me.  On a recent visit to Bressingham Gardens, Norfolk, I saw a beautiful Mahonia Aquiflorium Moseri.  I have searched several garden centres and no one can find me one of these.  Has anyone got any idea of where I might find one?  Bressingham Garden Centre lady said the specimen in the Gardens might be a trial.  Your suggestions would be very much appreciated.

Use the RHS Plant Finder online.  It allows you to enter a plant and then tells you which nurseries sell it in which regions and whether or not they do postal delivery.

http://apps.rhs.org.uk/rhsplantfinder/

Many thanks obelxx, your speedy response is most appreciated.  I will try your suggestion right now.

obelxx - have done the research as you suggested and was directed to two suppliers whom I have e-mailed.  Many thanks. Janie