Filament Spool Washer Bushing for 8mm Threaded Rod

I'm sure there is a ton of these, but I couldn't find one that I liked, maybe I'm not calling them the right thing.

Anywho, I'm brand new to 3D printing, and my first roll of filament is a 1/2kg roll of AIO brand black PLA. The inner part is 51mm. The spool holder that comes with the Anet A8 works, but the spool likes to go all over the place. So I printed a great spool holder from didesign ( http://www.thingiverse.com/thing:1743397 ) but sadly it didn't come with those washers pictured.