Some of the shops may have not provided a product feed. For this reason, the LinkDeli search function will not be able to retrieve products from these shops.
You are still able to add products from these shops to your own product library through the "add link" function or the bookmarklet (find out how you can manually add a product to your list here). As soon as they are added to your lib and lists, they behave like normal affiliate links and no further action is needed.
Please note that when adding links from the shops that provide a feed, any changes/updates to these products will be immediately reflected on your lists. On the contrary, your personal links will not follow any changes made to the original product link found on the site. Still, you can update the link manually from your dashboard and the change will propagate throughout all your lists the link is a member of.