You should be able to find a DG silencer. It was suppose to be as quiet or quieter than the stock silencer. I bet that will do you right. As a matter of fact, I'm 99% sure i've seen them at dirtoverstock. DG has always made very nice stuff, i'm sure you'd be happy with it!
J.
*edit*
Yup, i'm guessing this is the one you were looking at,
http://dirtoverstock.com/detail.aspx?ID=256
Should be a great unit, and comparable to the stock silencer if not a bit quieter. I have seen a few of these pop up used on ebay as well, so you may want to check there.