If you can use cheat codes, use the following codes:
[Change Trainer ID]
04100000 42935EE8 XXXXXXXX
04100000 429EC574 YYYYYYYY
04000000 027F1564 YYYYYYYY
Replace XXXXXXXX with your full ID (4-digit secret ID followed by 6-digit trainer ID) converted to hex, and YYYYYYYY with your 6-digit trainer ID converted to hex.