I’m not sure why you don’t have the option, but you might try a different version of Shrink that can use ImgBurn instead of DVDDecrypter.
This thread at afterdawn has a link to this version of Shrink. Read the first post: http://forums.afterdawn.com/thread_view.cfm/664041
Just replace the executable file in Shrink with this one you get from rapidshare.
ImgBurn is the updated burning engine from DVDDecrypter. Much more capable than Decrypter was at burning, and can make ISO’s as well. You’ll need to download and install it as well: www.imgburn.com ImgBurn and DVDDecrypter were both written by the same author, Lightning UK.