I'd also recommend renting a car from ORD versus waiting hours for a 135 mile flight to GRR. On the return flight, you will be waiting almost 12 hours to fly home.

Best prices seem to be United - consensus on this forum is that you will earn OP miles when flying *Alliance by December.

FWIW, it was $1347 TPE to GRR.

It is $1202 TPE to ORD. Continental has it for $2075.