I do have a personal plate that I too got before I joined my GLO. It's STL2MIL. If I could change it for free (which will never happen) I think I would get the plate with the Michigan State "S" on it and put behind it IGDLT since those plates with school letters on it can only have 5 letters/numbers on them.
Here's what it would look like if I did it. It looks really cool.
Sig Delt MI Plate