Did you find a solution for this? I still can't find it, and I have the same problem. I can't find the script (Example: 7262) to edit it and change the Pokeball item.
I tried to search for "FD 00 28 07 D1 0A 48" in the arm9.bin from Pokemon HeartGold that I extracted with the Nitro Explorer 3,
searching for it with HxD, but I cannot find that part.
Could it be some mistake of mine?