I have 2 Madone seat mast top caps in 20mm offset, both 135mm & 175mm in length. Both are new. NOT for the new Madone 9s, this is the round version.

I don't think I have the rail hardware anymore (you can just swap over what you have on there now), but can dig if needed. Will get pics up eventually, but they're new.

They retail for $140, I'll ship them for $85/ea.