More cost effective replacement Berkey filter wingnuts?

Does anyone know where to get more cost effective wingnut replacements for black berkey element filters? They’re $2.50 a piece plus $9 shipping on the berkey site (and similar sites as well), and cheaply made. If I knew the specs, I think I could just order a few non-berkey made wingnuts online for a much more reasonable price. Any tips from fellow berkey users?

If you can determine its width and thread type you maybe able to get a brass or stainless steel nut that fits.
Or purchase something else at the same time to reduce the impact of the minimum freight.