Active exhibit case ventilation

I have been asked by a client to duplicate an existing display case that has an active ventilation system. I don't know the source of this system but it is basically a box with a filter on one end, a fan inside and a small round piece of duct that plugs into a small round grill at the top of the case. Another round grill at the opposite end of the top acts as the exhaust from the case. Does anyone know of a company that makes these? Thanks for your thoughts.
Dincerely,
Dave Ryan