Go to the hardware emporuim and take a look at their various bolts. Find one that has roughly the same outside diameter, with a squared corner head, rather than a domed one. The head size should be larger than the 'head' of the guide rod. Find the kind that has the threaded portion near the end of its length. The unthreaded portion should be longer than the length of the guide rod.
Now, you cut off the threads with your Dremel wheel, or carefully with a hacksaw. This is where having some room for error on your part comes into play. Then, you chuck the cut end into a drill press so that you can begin to turn down the head with your files. Yes, you can use a portable drill secured by a vise; but, it's much more dicey on getting a good result. Work down the the flat portion of the head first, until it is at the thickness of the guide rod's. Then, you carefully work down the outside edge to match its diameter. Lastly, you finish the cut end as closely as possible down to the final overall length. Cold blue if desired, which I did.
I don't know if the bolt's heat treat(if any) will allow it to stand up to the pounding of the slide's recoil. Then again, if plastic suffices, there shouldn't be a problem.