Changing the region of a GBA transfer file?

[Air Conditioner]

I've got a special distribution iso from SEGA in the early 2000's they used at special events that would allow you to transfer an exclusive in-game item to Sonic Adventure DX or Sonic Adventure 2: Battle. This content as I've found is only transferable to Japanese copies of these games. I'm trying to convert this special ISO to transfer to USA copies of these games. I couldn't find any info on how to do something like this and I'm stumped after comparing hexfiles of the same names from the games and not finding anything I understood/saw as an indicator of region. Thanks to anyone who could offer insight on where I could go next.