keep an eye on the "for sale" sticky thread at the top of this forum. also craigslist.org, ebay.com and the talkbass classifieds are a good place to check. basscentral.com also has used sr5s from time to time.
Pretty much the fact that you've announced that your looking for one here should get you a few PM's with people willing to get rid of one. The last two that Ive bought I got that way!!