Sitemap & duplicate URL's
 

Does anyone know a way to allow duplicate URL's in a sitemap?

Here's my problem:

I'm designing (almost done) an online store with the following navigational
structure:

Home / Department / product listing / product detail.

Each department and product listing have unique pages but the product
detail
is a single page that is given a product ID parameter in the query string.

All pages are derived from a master page which has the siteMapPath control.

What I can't do is link from the product listing page to the product detail
page and show in the siteMapPath were the user has come from i.e.:

Home / Department / Product list /product detail

I’m aware that the default sitemap provider won’t allow duplicate URL’s.

I’d be grateful for some advice!