I have that same mill. Wonder if I'll get a free upgrade? I had to replace the thumb screws with some grade 5 bolts. Well I didn't have to, but it made it easier to adjust:)
http://www.monsterbrewinghardware.com/basehopper.html
Based on the info from their site the hoppers seem to be mill specific.
And they say that all products are in stock. So why not order one direct?