This premium effect, once exclusive to major publishers, is now achievable by any creator using professional custom holographic cards printing
The included holo card matches your pendant: common pendants come with a matching Pok Ball pattern holo card, while hidden pendants come with the corresponding Pokmon ex holo card
Alternatively, you can search for artwork online that aligns with your vision for the Pokemon card
I got the following email when I submitted and its been radio silence ever since lol
While there are a few creatures in the 99 that can help mitigate this problem, Id definitely recommend adding a few cards to help make sure that damage gets through during combat
For example, during a Throne of Eldraine Limited event, you can't add Seven Dwarves from your personal collection, no matter how happy they would be