Trade Summicron-M 28 f/2 ASPH for TRI-ELMAR WATE

I have a barely used, mint condition Summicron-M 28 mm f/2 ASPH and want to trade this lens for a TRI-ELMAR-M 16-18-21 mm f/4 ASPH.
The LEICA Summicron-M 28 mm f/2 ASPH is a barely used lens in perfect condition (as new!) 6- bit coded, in beautiful condition with boxes, cases, caps and hood. I cannot find any signs of use - but it has been used 3 times. Glass is clean and clear - I always kept a filter on it.
About a year ago I bought this lens new and haven't used it because I bought the new Summilux-M 35mm f/1.4 FLE. That's why I'm selling it. Now I want to go wider to compliment my set. Please contact me if you have a barely used TRI-Elmar 16/18/21 ASPH in mint condition and you want to trade this. Dependent on the condition of the TRI-Elmar and the availability of the finder, I am willing to pay for the extra difference.