It was only a matter of time. Official Sonic Adventure 2 plush toys have been made available for general purchase. The initial run seems to include Sonic (with SOAP Shoes), Tails, Shadow, Rouge and Hero Chao.
Check out the cool designs on the side there. If you want to grab one (or all) of them, then your best bet is to head to Wizzy Wig Collectibles and pre-order them. All but Shadow is available on the site, and they seem to cost around $15. Order them now.