There are many WEB sites, as well as CD-ROMs that serve this purpose. Some WEB sites even have multiple database searches, and provide comparison of search results. Here are a couple of web sites to help finding QSL managers. The list is not considered exhaustive. Portable operation should be sent to the 'native' country.
Cards made of lighter paper can easily be bent, damaged, or lost.
Heavier and out-sized cards unnecessarily add to the weight of the QSL packets. For want of this notification, some cards go through several bureaus before they reach the right one. Sometimes they never reach the operator. This will reduce the costs and storage space at the bureaus. We charge for extra cards.