A hardware tinkerer by the name of tschicki has created a fully custom PS2 Portable, even the mainboard is custom made, here is a quote from the source.
Source
Via
Just like the title says, this is a PlayStation 2 portable designed from scratch. This portable contains presumably world's first custom reverse engineered PS2 mainboard not made by Sony. It is only reusing 6 ICs of an original PS2, salvaged from SCPH-7900x or SCPH-9000x mainboards.
Most PS2 games can be played natively via OPL or NHDDL and the portable also features support for PS1 games via DKWDRV. Its two custom memory card slots are compatible with miniaturized PS2 Memory Cards, SD-Cards (MX4SIO) and a miniaturized SD2PSX.
Development of this project was started in 2022.
Source
Via