Precisions Arms at http://www.sniper-store.com/rifles.htm
had several in stock a few weeks ago when I was evaluating a potential 700P purchase. I believe they quoted around $30-35 each for them.
The magazine is the same as any Remington 700 DM magazine in the appropriate caliber. Most good sporting goods stores with gun sectionsor gun shops (or even WalMart) should have them.
