Here you go! This is a simple mod of the wallet.py file that automatically copies signatures to the clipboard.

To use it, make sure you are running Windows build 1.01e of Electrum,

 go to this directory: %AppData%\Electrum_SysFiles\1.01-e\C_\ElectrumPY\lib
 and replace the original wallet.py file in there with the one below:

Download
Size: 41686 bytes
SHA1: d18a4d273105a80a2e655ddabc2513dd004053ec

(for your info, the only source code changes are lines 477-478 and importing the Qt library - feel free to manually review the file if you're familiar with Python)