http://travelstarproducts.com/products.php
Is this the site you visited? It does say at the top of the page to contact them for products. The products shown are their recent projects.
I'll bet as long as they have the original mold, they might make a replacement tank for you. I would be cautious about trying one of the new tanks from TM simply because they have made slight changes to the frame over the years and a new one might not fit.