Not sure if you indeed need a customized version of that plugin or any custom code at all. What exactly do you want to achieve? The current behavior should be, that users always open the full-sized version when they click any thumbnail picture.
As I said, the download button needs to appear below each thumbnail image when browsing an album. This will allow users to automatically download the picture in fullsize without opening the pop up window and without right-clicking on it to save it. The plugin is already able to do such thing, it's just that it appears below the intermediate pictures and not below the thumbnails.
So yes, I need a customized version of this plugin. With the right knowledge, this should be quite easy to achieve.
Budget: $20. Time schedule: unsure, but I believe 2 days is enough.