I have a situation that I am hoping that some very savy travellers can offer advice as to the best way to cover this situation, so that i dont loose money - If I can make miles even better.

I fly out of PDX. I am Prem Ex on UA (150,000 miles), and just an ordinary member on Alaska (63,00 miles).

I have a situation that MAY need me to be in Maui on April 25th, just the one day from 9-5 (so I can arrive on the Saturday and leave Monday) I wont know until 14 or 15 days prior whether I will actually be required to go to Maui. I will only be reimbursed $500.

Obviously I can use FF miles on AS or UA, and fly on them or Hawaiian. My dilema is that 40,000 miles for $500 is not a very good exchange. Does anyone have any creative alternatives?