I think what you are looking for is the IWW Wildcat. From what I can tell, the CNT's symbol is not a cat, but a red and black flag. (See the InfoShop Anarchist FAQ.) The same FAQ mentions a "wildcat" inspired by the IWW. (The IWW is the Industrial Workers of the World, a labor union that seeks to dismantle capitalism. I can't quite tell if they're anarchist - the website says: "The IWW is a revolutionary industrial unionist organization, and its membership includes radicals of every stripe, including anarchist, communist, socialist, syndicalist, etc.")

Anyway, the IWW t-shirt is available here: http://www.iww.org/store/shirts. The CNT red and black flag is available on t-shirts here: http://www.cafepress.com/buy/anarchism/-/pv_design_details/pg_1/id_8898114/opt_/fpt_.