There are several versions. Some fully stainless, including stainless thrust washer. The different versions:
lever: stainless steel, steel, aluminum, plastic
cam: stainless steel, steel
thrust washer: stainless steel, plastic
bolt: stainless steel, steel

They range from 5 to 10 euro depending on which material you choose. But orders under 50 eur has a 15 eur surcharge. orders under 100 eur have a 5 eur surcharge.

I tried looking up Japanese Misumi cam levers, but they appear to be more expensive, although there is no minimum order quantity and shipping is free, but I'm sure they won't be happy if you use the free shipping for a few dollars of items.

Kipp has a nice selection of mechanical parts if you ever need to build some stuff. Misumi has some good stuff too, like ultra low head Japanese bolts that you can't find anywhere else (much bigger selection with more various purposes, plus custom CNC parts ordered to size). Misumi does stock precision NTN cartridge bearings if you want to change the ones in your hubs.