routing with encoded forward slash

[eluser]enition[/eluser]
Can any one help me with a work around for this;

I have an external url pointing to a module on my site, this url contains a code for a product part. Problem is that this part contains and encoded forward slash (/), I can get the rout working fine if the code was a proper unencoded slash using one of the following:

Code:

$route['product/(:any)/(:any)'] = "product/lookup/$1--$2";
$route['part/([a-zA-Z0-9]+)/([a-zA-Z0-9]+)'] = "product/lookup/$1--$2";

this works fine with a regular forward slash and as you can see will have to convert the '- -' back to a / inside the module. But as soon as I use / it stops working and I get a 404..

here is an example url that I need to work: http://www.test.com/product/product/one

but i need to pass the 'product/one' as a variable to product/lookup..

any pointers as to how I could achieve this better.. bearing in mind that not all products have the encoded forward slash.

I am rubbish at expressions so go easy

Thanks,
Adam