Jenna,

There is a company here in Brazil that fabricates 22,5lts plastic tanks for Xt660s. See the link bellow:

http://www.gilimoto.com.br/detalhes....25&produto=179

It costs R$ 550 which is around 330 USD. I'm not sure how the shipping works. Let me know if you need any help with translation.

Cheers,
Leandro