XML sitemap for database-driven web stie

I have a site that uses a MySQL database to populate pages with data. I need a way to create a sitemap and it needs to be fairly fast and not a big resource drain. It needs to be run every day because the content of my site changes many times a day. Some records last longer, but many of the records that generate pages are short term. I have looked at and tried some of the boxed solutions out there with no success. I am open to suggestion and want bids only from people with experience with sitemaps for dynamic sites. My site contains coupons. There are about 8000 coupon records from about 800 stores at this time, but it needs to scale because the site will grow over the next few months. Thanks