u could use photoshop and just go to image->image size and edit it to how many pixels you want. the only problem is that it will make the entire picture smaller. but it sounds like you don't wanna stretch or compress this picture.
i had some free time so i designed a small sig. if you like it then use it. if you don't u don't have to. i also still have the original psd if you want me to change it. enjoy!