Try making original parts instead. Have you considered doing kid parts? It's an untapped market as there's only like 2 official DLCs for child characters.
There's also a market for face parts that let you create characters of different ethnic groups.
I'm especially interested if you can create parts of the same style and quality as these ones. https://forums.rpgmakerweb.com/index.php?threads/mons-character-generator-expans...
If you're any good at TV parts and SV battlers, you could make a lot of money creating animals too. They basically don't exist as paid or free assets.