I've got a Wordpress plugin that does this in development but its pending on the original cart developer accepting it.
My modifications come from my data import plugin Easy CSV Importer. Easy CSV Importer will import lets say 500,000 rows of data, create a page for each product/row, add each product to the shopping cart data and place the products own add to cart button on the page with cross references within the data.
Then shoppers can add affiliate products to the shopping cart. On checkout it will build a url which sends all submitted products to the sellers site and adds to the shoppingcart.
There are complications. If the products are from one provider that is fine. If it is a mix then the plugin will need to open multiple windows, one for each website. That could end up being 2-3 who knows in some purchases it might be more.
The option to trigger the openining of each products on its own sales page will be provided. Not the best approach but at the end of the day the chance of affiliate commission is still high and this approach is legit.
Easy CSV Importer is a read to buy plugin and the cart is almost done.