Silver isn’t my first choice but Amazon has the Rotring 600 0.7mm silver for $18.29 right now.
I prefer the feel and look of the 0.7mm more than 0.5 or smaller. I recommend just googling rotring 600 and click the shopping tab once in a while. I’ve gotten a black and blue for $18-19 and I’ve seen the silver and red versions pop up pretty frequently at the same price.