PS2 - Modchip to just disable disk drive region lock?

Are there any PS2 modchips out there that are only to disable to region-locking on the drive chip and/or a way to connect chips such as the ModBo to only do this? I use FreeHDBoot (hard drive variant of FreeMCBoot) on my ps2 and am perfectly fine with how it operates, but I have some Japanese PS1 games that I haven't been able to get working through homebrew methods and would like to be able to play them.

 

either popstarter or http://assemblergames.com/l/threads/750x-for-12f629-12f683.62871/