The choke tubes sold for Winchester/Weatherby/Mossberg/Browning (Invector)will fit the T/C. They are a little shorter as in they are not flush with the muzzle when installed,but slightly below it, but they seem to work fine. A lot cheaper than T/C tubes.
http://www.cabelas.com/cabelas/en/templates/links/link.jsp?id=0012776210873a&type=product&cm Cat=search&returnPage=search-results1.jsp&No=20&noImage=0&Ntt=choke +tube&Ntk=Products&QueryText=choke+tube&am p;Ntx=matchall&N=4887&Nty=1