Here in Western NY there is Schicthels Nursery, Concord Nursery, Wheelock & Turnbull Nursery for sure and possibly Akron Tree Farms, Russells Nursery. There got to be a pile in Ohio. I would check it out at www.onla.org. In actuality there should be a pile of these in PA also but you should know better than I on that. The willows are probably going to be harder to find than other stuff as only us crazy zoo people want them.  Also – you might call Horticultural Associates in Rochester who are plant brokers, ask for Dave McGowan and let them do the legwork for you  www.wefindplants.com  - Steve