Looking back at his Twitter (X), in the past he said that "Eri Ayase" was a work by Lutsuki, and recently he improved it himself.Suika626、投稿: 12533960、メンバー: 6656802 said:You must be registered to see the links
このラブライブカードの作者、またはどこで入手できるか知っている人はいますか
It is written that the past works of “Umi Sonoda” and “Hanamaru Kunikida” were created by “西木野真姫(users/26156793)”.
This also seems to have been improved by him recently.
In other words, you can't get the card itself. Or you can get it if you ask him directly and he approves.