...then you may want to check out this link to a site found by one of our friends in class. This brush looks very comparable to the brush I use in class, and as you already know, they are spendy brushes.
In my opinion, the synthetic alternatives don't come close in ability to hold large volumes of water and also overall softness of the brush.
These brushes are useful not only for laying down clear water before putting in a blended or other wash, but they are great for glazing over with clear water to fix problems or with paint to enrich colors without disturbing the bottom layer.
The 2" brush sells for something like $80 which is A LOT but there's a way to get a 10% discount and free shipping if you accept an offer to let them send you marketing emails.