the chinese trade companies are still using modified forms pushed out by the former ministry of foreign trade, which in many cases are not applicable any more. in in essence they cover a lot of grounds for legal loop wholes.
the american trades are some what different although 1 out of 9 americans is a lawyer.
therefore you would just have to take a chinese standardized form (available from any "import/export co in china) and to modify it by taking out where does not apply and adding to suit yours.
what also may change is the trading partners country...
what's the subject of trade also changes the picture: technology trade? merchandize only? services...?
in my opinion it is hard to just grab some form and use it. the legal risks you would undertake does not really justify the cost saving over a lawyer in the right field.
