I bought a y-pipe for my old 4th gen from a place in Canada called budget Exhaust, but that was back around 2004. Not sure if they are still around or if they still make the y-pipe, but might be worth the time to look into it.
If you can isolate where the noise is coming from, you should be able to quiet is down some. If the pipe has a small hole, you can try using some moldable JB Weld and covering it with some header wrap once it's dried.
Or if the hole is in a straight run of pipe, you could try putting one of the clamps over it.
